bluuebunny/crossref_metadata_2025 huggingface dataset:
STIMULATION OF GASTRIC OSMORECEPTORS BUT NOT THE SODIUM MONITOR INCREASES RENAL ANGIOTENSIN‐CONVERTING ENZYME ACTIVITY
Authors: Ye VZC , Duggan KA
Published: June 2007

1. Stimulation of the gastric sodium monitor has been reported to cause a decrease in renal nerve activity and also a decrease in plasma renin activity in renal venous blood. This suggests that changes in sympathetic nerve activity and in the intrarenal renin‐angiotensin system may mediate the natriuresis that occurs following gastric sodium administration. In the present study we sought to determine whether gastric sodium administration also modulates angiotensin‐converting enzyme (ACE) activity in the kidney.

2. Male Sprague‐Dawley rats were equilibrated on a low‐sodium (0.008%) diet for 7 days. On the day of the experiment, rats were anaesthetized and kidneys were harvested and immediately snap frozen at 0 and 60min after intragastric administration of a saline load (1.5 mmol/kg as 3 mol/L saline) or an equivalent volume of iso‐osmotic urea (5.95%). Angiotensin‐converting enzyme activity was determined by incubation of kidney homogenates with hippuryl‐histidyl‐leucine and fluoro‐metric assay of the histidyl‐leucine generated.

3. Angiotensin‐converting enzyme activity in the kidney increased in response to the intragastric administration of both sodium chloride and urea. Angiotensin‐converting enzyme activity increased significantly from control levels (189.9 ± 24.3 nmol/min per g protein) by 60 min in both NaCl‐ and urea‐treated groups (492.3 ± 27.3 and 468.6 ± 28.7 nmol/min per g protein, respectively; P < 0.0005).

4. We conclude that instillation of sodium chloride or iso‐osmotic urea into the stomach increases ACE activity in the kidney. The results of the present study suggest that this effect is due to changes in osmolality rather than stimulation of the gastric sodium monitor.
EFFECTS OF ADRENALINE INFUSION ON PLASMA LIPIDS AND NORADRENALINE LEVELS IN RABBITS WITH ADRIAMYCIN‐INDUCED CARDIOMYOPATHY
Authors: Minatoguchi Shinya , Uno Yoshihiro , Seishima Mitsuru , Koshiji Masatoshi , Kakami Masao , Yokoyama Hitomi , Ito Hiroyasu , Fujiwara Hisayoshi
Published: June 2007

1. We investigated the acute effects of adrenaline infusion on plasma lipid levels in vehicle‐ and adriamycin‐treated rabbits. Lipids were measured before and 30 and 60 min after the commencement of continuous intravenous administration of adrenaline (0.06 |xg/kg per min) or saline in pentobarbital‐anaesthetized rabbits.

2. Adrenaline infusion significantly increased plasma free fatty acid (P < 0.05) and noradrenaline (NA) levels (P < 0.05) in vehicle‐treated control rabbits, but not in adriamycin‐treated rabbits. However, adrenaline had no effect on plasma total cholesterol, free cholesterol, high‐density lipoprotein‐cholesterol, triglyceride or phospholipid levels.

3. Pretreatment with propranolol almost completely inhibited increased plasma free fatty acid and NA levels associated with adrenaline infusion, suggesting that adrenaline increases plasma free fatty acid and NA levels via the stimulation of p‐adreno‐ceptors in vehicle‐treated rabbits.

4. It is suggested that both the production of plasma free fatty acids and the release of NA via the activation of β‐adrenoceptors is reduced in rabbits with adriamycin‐induced cardiomyopathy. This may be related to the down‐regulation of β‐adrenoceptors caused by elevated plasma NA levels induced by cardiac failure.
EFFECTS OF SARAFOTOXIN S6c ON RENAL HAEMODYNAMICS AND URINE FORMATION IN ANAESTHETIZED DOGS
Authors: Matsuo Gen , Matsumura Yasuo , Tadano Kiyoshi , Hashimoto Takashi , Morimoto Shiro
Published: June 2007

1. The effects of sarafotoxin S6c (S6c), a selective endothelin ETB receptor agonist, on renal haemodynamics and urine formation were examined in anaesthetized dogs.

2. Intrarenal arterial infusion of S6c at a rate of 1 or 5 ng/kg per min produced a transient increase in renal blood flow (RBF), with no change in systemic blood pressure and heart rate; RBF then decreased gradually to below the basal value. There were significant and dose‐dependent increases in urine flow and free water clearance and decreases in urine osmolality during S6c infusion, whereas urinary excretion of sodium and glomerular filtration rate (GFR) remained unchanged. Simultaneously, S6c administration elicited a marked increase in urinary excretion of nitric oxide (NO) metabolites, N02− and N03− (UNO*V).

3. In dogs simultaneously administered S6c (5 ng/kg per min) and iVG‐nitro‐L‐arginine (NOARG; 40 (jig/kg per min), a NO synthase inhibitor, the renal vasodilator effect of S6c was abolished and marked reductions in RBF and GFR were observed. The S6c‐induced diuretic action was not affected by NOARG. In the presence of NOARG, there was a small amount of UNOxV at the basal level and the administration of S6c did not increase UNOxV.

4. These results suggest that an intrarenal arterial infusion of S6c enhances the production of NO in the kidney and that this enhancement contributes to the peptide‐induced renal vasodilation. In contrast, it is unlikely that S6c‐induced water diuresis is related to NO production stimulated by this peptide.
COMPETITION OF ADENINE NUCLEOTIDES FOR A l,3‐[3H]‐DIPROPYL‐8‐CYCLOPENTYLXANTHINE BINDING SITE IN RAT VAS DEFERENS
Authors: Smith Andrew D. , Cheek Dennis J. , Buxton Iain LO , Westfall David P.
Published: June 2007

1. The binding of l,3‐[3H]‐dipropyl‐8‐cyclopentylxanthine ([3H]‐DPCPX), a specific adenosine Ai receptor antagonist, was examined in rat vas deferens membrane preparations using radioligand binding techniques.

2. l,3‐[3H]‐Dipropyl‐8‐cyclopentylxanthine bound to these preparations with a KD of 1.07 ± 0.14 nmol/L (n = 6). The density of [3H]‐DPCPX binding sites was 133.38 ± 5.57 fmol/mg protein.

3. Computer analysis indicated that nucleosides competed for [3H]‐DPCPX binding at two distinct sites. The rank order of potency at the higher affinity site corresponded to R‐phenyliso‐propyladenosine (R‐PIA) 2‐chloroadenosine (2‐CI ADO) cyclopentyladenosine (CPA) N‐ethylcarboxamidoadenosine (NECA)>s‐phenylisopropyladenosine (s‐PIA). Kj values were in the low nmol/L range. The rank order of nucleoside potency at the lower affinity site corresponded to R‐PIA CPA NECA>=2‐ClADO> S‐PIA. Ki values were in the low μmol/L range.

4. Nucleotides competed for [3H]‐DPCPX binding at a single site only. The rank order of potency at this site corresponded to a,β‐methylene ATP βγ‐methylene ATP = ATP. Ki values were in the high |xmol/L range. This site seemed to correspond with one of the two binding sites predicted by nucleoside competition binding.

5. The ATP‐regenerating compound myokinase did not significantly change the competition curve for ATP, indicating that the competition for [3H]‐DPCPX binding observed in the presence of ATP was due to an effect of ATP per se and not to an action of a degradation product.

6. The results demonstrate that in rat vasa deferentia there exist two distinct binding sites for [3H]‐DPCPX. One of these sites binds only nucleosides and may represent an adenosine Ai receptor, as usually defined. The other site binds both nucleosides and nucleotides and may represent an atypical adenosine A1 receptor, an atypical P2 or a P3 purinoceptor.
LONG‐TERM EFFECT OF MANIDIPINE ON RENAL FUNCTION AND STRUCTURE IN UNINEPHRECTOMIZED SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Fujimaki Michitaka , Nagase Mitsumasa , Uchida Shunya
Published: June 2007

1. Long‐term effects of manidipine hydrochloride (MAN), a calcium channel blocker, were examined in three groups of spontaneously hypertensive rats (SHR). Group 1 was given uninephrectomy (UNX) and MAN treatment, group 2 was given UNX and was not treated with MAN and group 3 was given neither UNX nor MAN treatment

2. At week 15 after UNX, inulin clearance in group 1 rats decreased compared with rats in groups 2 and 3, but remained at the same level at week 40, when the level in group 2 rats declined below that in rats in groups 1 and 3.

3. Glomerular and tubulointerstitial lesions did not differ at week 15 after UNX among the three groups, whereas at week 40 both were advanced in the order of groups 2,1 and 3.

4. Proteinuria did not differ between rats in groups 1 and 2 over the experimental period.

5. At week 15, the kidney weights of group 1 rats were greater than those of group 2 rats, indicating more prominent tubular hypertrophy in the former group. This was confirmed by morphometry of the proximal tubuli. In contrast, the glomerular volumes of rats in groups 1 and 2 were enlarged compared with that of rats in group 3, with no difference between the former two groups.

6. The findings suggest that MAN exerts renoprotective effects in SHR, both with regard to function and morphology. An effect on glomerular haemody naniics was considered to more likely be the mechanism underlying the renoprotective effect of MAN rather than that of a lowering of systemic blood pressure.

7. Augmented tubular hypertrophy after MAN treatment was an unexpected finding of the present study and the biological significance of this finding remains to be explored.
THE EUGLYCAEMIC HYPERINSULINAEMIC CLAMP: AN EVALUATION OF CURRENT METHODOLOGY
Authors: Morris Andrew D. , Ueda Shinchiro , Petrie John R. , Connell John MC , Elliott Henry L. , Donnelly Richard
Published: June 2007

1. The recognition of the role of insulin resistance in disease states and the recent development of new drugs that modify insulin‐dependent metabolism has led to increased use of the euglycaemic hyperinsulinaemic clamp to measure in vivo insulin sensitivity, but several key aspects of the technique are poorly documented in the literature.

2. We have evaluated the reproducibility and intersubject variation of measurements of insulin sensitivity in groups of insulin‐sensitive and insulin‐resistant subjects and assessed the effects of hand warming on haemodynamic and metabolic responses.

3. Subjects participated in one of two protocols: (i) 18 healthy male volunteers and 18 patients with hypertension and glucose intolerance were clamped on two occasions, 1 week apart with measurements of insulin sensitivity (M) derived after 120 and 180 min of hyperinsulinaemia; and (ii) six healthy volunteers were clamped on one occasion with simultaneous sampling of antecubital and ‘arterialized’ (dorsal hand) venous blood for comparison of plasma glucose concentrations and oxygen saturation and a further six volunteers were clamped on two occasions with and without the use of hand warming.

4. Measurements of M derived after 120 min (M120) and 180 min (M180) of hyperinsulinaemia were reproducible: the coefficients of repeatability (mg/kg per min) of M120 and M180 were 1.0 and 0.9 for volunteers and 1.0 and 1.0 for the patient group, respectively. The intersubject variation in insulin stimulus was high: coefficients of variation for M180 were 22% for volunteers compared with 38% for the patient group. In volunteers compared with the patient group, hand warming significantly increased venous oxygen saturations (95 ± 2 vs 79 ± 18%, respectively) and glucose concentrations (5.2 ± 0.2 vs 4.5 ± 0.4 mmol/L, respectively) and measurements of M were significantly higher using arterialized compared with antecubital venous blood. However, local hand warming was associated with systemic vasodilatation: blood pressure decreased (e.g. 6mmHg diastolic; P < 0.05) with a compensatory increase in heart rate (8 b.p.m.).

5. In conclusion, clamps of 120 and 180 min duration yielded measurements of M that were reproducible. The technique is much more robust when used in the context of a crossover design because of the significant (20–40%) intersubject variation in M, even among apparently homogeneous male volunteers. Hand warming effectively arterializes venous blood and gives significantly higher M values, but induces systemic vasodilatation, which may confound measurements of M.
CHARACTERISTICS OF MEMBRANE TRANSPORT PROCESSES OF MACULA DENSA CELLS
Authors: Bell P Darwin , Lapointe Jean‐Yves
Published: June 2007

1. Macula densa (MD) cells are located within the thick ascending limb (TAL) and have their apical surface in contact with tubular fluid and their basilar region in contact with the glomerulus. These cells sense changes in luminal fluid sodium chloride concentration ([NaCl]) and transmit signals resulting in changes in vascular resistance (tubuloglomerular feedback) and renin release.

2. Current efforts have focused on understanding the cellular transport mechanisms of MD cells. Progress in this area has benefited from the use of the isolated perfused TAL‐glomerular preparation, which permits direct access to MD cells.

3. Using microelectrodes to measure basolateral membrane potential (VBL) of MD cells, it was found that VBL was very sensitive to changes in luminal fluid [NaCl]. As [NaCl] was elevated from 20 to 150mmol/L, VBL was found to depolarize by over 30 mV.

4. Basolateral membrane potential measurements were also used to identify an apical Na+: 2CI−: K+ cotransport pathway in MD cells that is the major pathway for NaCl entry into these cells.

5. Other work identified a basolateral chloride channel that is presumed to be responsible for changes in VBL during alterations in luminal [NaCl]. This channel, which is the predominant conductance across the basolateral membrane, may be regulated by intracellular Ca2+ and cAMP.

6. An apical Na+: H+ exchanger in MD cells was detected by measuring changes in intracellular pH using the fluorescent probe 2′,7′‐bis‐(2‐carboxyethyl)‐5(and‐6) carboxyfluorescein.

7. Using patch‐clamp techniques, a high density of pH‐ and Ca2+‐sensitive K+ channels was observed at the apical membrane of MD cells.

8. Other studies found that, at the normal physiological conditions prevailing at the end of the TAL (luminal [NaCl] of 20–60 mmol/L), reabsorption mediated by MD cells is very sensitive to changes in luminal [NaCl].
SOCIAL ISOLATION AFFECTS THE PATTERN OF CARDIOVASCULAR RESPONSES TO REPETITIVE ACOUSTIC STARTLE STIMULI
Authors: Blanc J. , Baudrie V. , Tulen J. , Ponchon P. , Gaudet E. , Elghozi JL
Published: June 2007

1. The aim of this study was to investigate the cardiovascular responses to repetitive alerting stimuli in rats subjected to intermittent social isolation, in comparison with animals housed in pairs.

.2 Ten male Wistar rats were implanted with a blood pressure (BP) telemetric system and enrolled in a randomized cross‐over study design. Rats were either isolated or housed in pairs for an 8 day period. At the end of each period, the animals were exposed to five acoustic stimuli (110 dB at 15 kHz, 80 ms after the impact, duration 700 ms) at 60 s intervals. For each stimulus, maximal BP and heart rate (HR) responses were calculated. BP variability was analysed in the frequency domain before the first stimulation using power spectral analysis.

3. Isolated animals showed more faster breathing (1.71 vs 1.42 Hz in the paired condition). The 0.4 Hz zone of the systolic BP spectral power was not significantly affected by isolation (1.11 vs 0.85 mmHg2). BP and HR resting levels of isolated rats (121 mmHg for the systolic BP and 290 b.p.m.) were similar to those of animals housed in pairs (119 mmHg for the systolic BP and 279 b.p.m.).

4. The first acoustic stimulus caused a brief rise in BP of a comparable amplitude in both conditions (24 ± 2 mmHg). A biphasic HR response was also observed, but the delayed bradycardia was more marked during isolation (37 vs 6 b.p.m. decrease). BP and HR levels were restored within 20 s.

5. Interestingly, BP responses were progressively attenuated to become negligible at the fifth presentation (1 mmHg) in the isolated state, while during the paired state a substantial pressor response (13 mmHg) after each successive stimulus was maintained. Paired rats exhibited a constant HR profile across the trials, consisting in a slight HR increase (< 5 b.p.m.), concomitant with the BP elevation, followed by a delayed bradycardia (around 15 b.p.m.). HR profiles in the isolated condition differed markedly: HR rises increased in magnitude with the trial number, reaching 30 b.p.m. after the 5th trial.

6. Spontaneous BP and HR increases, as observed throughout the experiment were quantitatively small (6 mmHg and < 10 b.p.m.) in the two conditions.

7. These data indicate that isolation markedly affects the BP habituation profile to repetitive alerting stimuli. The BP response attenuation might unmask a tachycardic response. Alternatively, the amplified tachycardia following the latter stimuli might express sensitization to the conditioned fear resulting from isolation.
INVOLVEMENT OF NON‐NMDA AND NMDA RECEPTORS IN GLUTAMATE‐INDUCED PRESSOR OR DEPRESSOR RESPONSES OF THE PONS AND MEDULLA
Authors: Chen SY , Wu WC , Tseng CJ , Kuo JS , Chai CY
Published: June 2007

1. Fifty‐five intact and six baroreceptor denervated and vagotomized cats of either sex were anaesthetized intraperito‐neally with urethane (400 mg/kg) and a‐chloralose (40 mg/kg). Responses of the systemic arterial pressure (SAP), mean SAP (MSAP) and sympathetic vertebral nerve (VNA) and renal nerve activities (RNA) were recorded.

2. In intact animals, monosodium L‐glutamate (Glu, 0.1 mol/L, 50 nL) was microinjected into pressor areas of the locus coeruleus (LC), gigantocellular tegmental field (GTF), rostral ventrolateral medulla (RVLM) and dorsomedial medulla (DM), and the depressor areas of caudal ventrolateral medulla (CVLM). The induced actions were compared before and after microinjection of either glutamate antagonists, glutamate diethylester (GDEE, 0.5 mol/L, 50–100nL), a competitive AMPA receptor blocker, or 2‐amino‐5‐phosphonovaleric acid (D‐AP5, 0.025 mol/L, 50–100 nL), a competitive N‐methyl‐D‐aspartate (NMDA) receptor blocker. GDEE completely blocked the increases of SAP and VNA elicited from all pressor areas. D‐AP5 only partially blocked the pressor but slightly blocked VNA and RNA responses from LC, GTF and DM, particularly those from RVLM. Neither GDEE nor D‐AP5 blocked the depressor responses of SAP and two nerve activities elicited from CVLM.

3. In baroreceptor denervated animals, NMDA (2 mmol/L, 50–100 nL) and AMPA (0.2 mmol/L, 50–100 nL) were micro‐injected into the same pressor areas of GTF, RVLM and DM and the depressor area of CVLM responsive to Glu activation (0.1 mol/L, 30 nL). In RVLM, DM and CVLM, the results of either NMDA or AMPA were similar to those induced by Glu. However, in GTF, microinjection of either NMDA or AMPA did not induce similar responses to Glu. This suggests that the nature of GTF may differ from RVLM and DM.

4. The above results suggest that the Glu‐induced pressor responses from LC, GTF, DM and especially RVLM, are primarily mediated through AMPA receptors. The Glu‐induced depressor responses from CVLM may not be predominantly mediated by either AMPA or NMDA receptors.

5. In both baroreceptor‐intact and ‐denervated cats stimulation of the pressor areas often produced an increase of VNA and a decrease of RNA, while in the depressor CVLM decreased both VNA and RNA. The VNA, but not RNA were positively correlated with the pressor responses, while both VNA and RNA were positively correlated with the depressor responses. This may suggest that neurons of the sympathetic vertebral and renal nerves are topographically organized in the brain.
HORMONES AS LONG‐TERM ERROR SIGNALS FOR THE SYMPATHETIC NERVOUS SYSTEM: IMPORTANCE OF A NEW PERSPECTIVE
Authors: Osborn John W.
Published: June 2007

1. A hormonal‐sympathetic reflex model for long‐term control of arterial pressure is presented. It is hypothesized that the hormonal‐sympathetic reflex regulates arterial pressure during chronic dietary salt loading by decreasing sympathetic tone. This sympathetic response is mediated by an increase in plasma vasopressin (AVP) and a decrease in plasma angiotensin (AngII).

2. Three new models of neurogenic salt‐dependent hypertension are presented. All models are theoretically based on an impaired hormonal‐sympathetic reflex.

3. In the first model, sympathetic responsiveness is ‘clamped’ by long‐term α‐adrenergic blockade with prazosin. Prazosin treated rats exhibit marked salt‐dependent hypertension despite normal suppression of the renin‐angiotensin system.

4. In the second model, the ability of the central nervous system to respond to salt‐induced changes in AVP and AngII concentrations was prevented by long‐term administration of antagonists selective for the AVP‐V1 and AT1. This ‘clamp’ of the afferent hormonal signal resulted in salt‐dependent hypertension identical in magnitude to that observed in prazosin treated rats.

5. In the third model, the long‐term arterial pressure responses to increasing dietary salt were examined in sino‐aortic denervated (SAD) rats. SAD rats exhibited salt‐dependent hypertension, of lesser magnitude than that observed with ‘clamped’ afferent and efferent pathways of the hormonal‐sympathetic reflex.

6. A primary role for hormonal ‘error signals’ is presented and the impact this perspective has on past and future investigations of central mechanisms of long‐term arterial pressure regulation is discussed.
CIRCULATING Na+/K+‐ATPase INHIBITORS: EFFECTS OF NEUROPEPTIDES, VOLUME EXPANSION AND SALT LOADING IN CONSCIOUS RATS
Authors: Schmitt Bernhard M. , Unger Thomas , Rettig Rainer
Published: June 2007

1. In mammalian plasma, many different inhibitors of Na+/K+‐ATPase are present, but it is not clear whether their net effect on Na+/K+‐ATPase activity changes during the regulation of electrolyte and fluid balance. We studied Na+/K+‐ATPase inhibition by plasma extracts in conscious rats during short‐and long‐term body fluid regulation.

2. Male, adult, conscious, freely moving Wistar rats were subjected to one of the following protocols: (i) intracerebroventricular (i.c.v.) injections of angiotensin II (Angll; 1, 10 and 100 ng), the Angll receptor antagonist losartan (1μg), atrial natriuretic peptide (ANP‐III; 1μg) or isotonic saline (IS); (ii) intra‐arterial (i.a.) injections of IS (6 or 10 mL), hypertonic saline (HS; 1.2% NaCl, 5 mL) or hypertonic plasma expander (HPS; 3.5% hetastarch in HS, 5mL); or (iii) a low salt‐high salt‐low salt diet sequence (0.18/1.8/0.18% NaCl chow for S days each with controls receiving 0.18% NaCl on all days). Bodyweight, the intake of food and water, urine volume and Na+ concentration and weight of faeces were determined daily. Plasma samples were withdrawn repeatedly throughout the respective protocols, extracted on C18‐reversed phase columns and assayed for their effect on the activity of different Na+/K+‐ATPase preparations.

3. The inhibition of rat brain Na+/K+‐ATPase by plasma extracts was not significantly changed by i.c.v. injection of Angll, losartan, ANP‐III and IS within the observation period (30 min from respective stimuli). Similarly, no significant changes occurred after acute volume expansion by i.a. injection of IS or HS within 120 min; upon HPS, however, Na+/K+‐ATPase inhibition was decreased by approximately 20% (P<0.05), probably due to passive dilution. During the high‐salt diet, fluid retention was effectively counteracted by an adaptive increase of urinary sodium excretion. Throughout the protocol, inhibition of pig brain Na+/K+‐ATPase by plasma extracts did not differ significantly between groups.

4. It is concluded from these results that the short‐ or long‐term control of body fluids in conscious rats is not associated with systematic changes in Na+/K+‐ATPase inhibition by plasma factors.
EFFECT OF NG‐M0N0METHYL‐L‐ARGININE ON THE MICROCIRCULATION OF RAT SKIN
Authors: Kakizoe Eiichi , Kobayashi Yuta , Okunishi Hideki , Shimoura Keiko , Jidoi Joji , Hattori Keisuke
Published: June 2007

1. The effects of NG‐monomethyl‐L‐arginine (L‐NMMA), a nitric oxide (NO) synthase inhibitor, on the microcirculation of rat dorsal skin were studied to examine the role of NO in the regulation of regional haemodynamics.

2. The blood volume in the skin microcirculation, which was continuously measured by reflectance spectrophotometry, was significantly decreased in response to L‐NMMA (10 mg/kg bodyweight, i.v.), suggesting vasoconstriction, and the response continued for more than 20 min. In contrast, the increase in systemic blood pressure (BP) disappeared soon after administration of L‐NMMA.

3. These results show that L‐NMMA elicits long‐lasting responses in the skin microcirculation, whereas the systemic BP rapidly recovers, suggesting a large contribution of the NO system to the regulation of rat skin microcirculation.
INCREASED KALLIKREIN ACTIVITY IN THE RABBIT RENAL VASCULATURE DURING LOW SODIUM INTAKE
Authors: Kuo Jay J. , Zimmerman Ben G.
Published: June 2007

1. Vascular tissue has been shown to possess a kallikrein ‐kinin system that may participate in the kinin‐mediated increase in renal sodium excretion. As sodium deprivation has been demonstrated to increase kallikrein content in the kidney and urine we hypothesized that during low sodium intake, kallikrein should increase in the renal vasculature.

2. Kininogenase activity, reflecting kallikrein enzymatic content, was measured in a homogenate of a microdissected intrarenal arterial network (IAN) from the rabbit kidney. Kininogenase activity was determined in rabbits on a normal sodium (n= 14) or sodium‐restricted (n—9) diet.

3. Total kininogenase activity in rabbits on a normal sodium diet was 15.0 ± 2.7 pg kinin/mg per 30 min, while it was much higher in rabbits on a sodium‐restricted diet (90.7 ± 16.5 pg kinin/mg per 30 min). Specific tissue kallikrein activity was measured by comparing the difference in kininogenase activity in homogenates treated with soybean‐trypsin inhibitor (SBTI) compared with homogenates treated with SBTI and aprotinin. This difference was much larger in the sodium‐restricted rabbits than in rabbits on a normal sodium diet (29.5 ±3.8 vs 5.1 ± 1.7 pg kinin/mg per 30 min, respectively).

4. We conclude that the rabbit IAN produces kallikrein, which is markedly increased in response to sodium restriction. Increased kinins during sodium restriction may modulate the pressor and anti‐natriuretic systems activated during negative sodium balance.
LACK OF EFFECT OF AGE ON THE CARDIOVASCULAR RESPONSE TO NEUROPEPTIDE Y INJECTION IN THE RAT NUCLEUS TRACTUS SOLITARIUS
Authors: Morris Margaret J. , Pavia Jillian M.
Published: June 2007

1. Neuropeptide Y (NPY) is colocalized with catecholamines in central regions involved in blood pressure regulation and exerts depressor responses in the nucleus tractus solitarius (NTS). Ageing is accompanied by a decline in baroreflex function and a reduction in NPY concentrations in some brain areas. The present study investigated whether the cardiovascular response to NPY microinjection into the NTS and medullary NPY concentrations were conserved in aged rats.

2. Neuropeptide Y (6 pmol in 100 nL) unilaterally injected into the NTS of anaesthetized 3‐ or 17‐month‐old male Sprague‐Dawley rats produced a prompt 9–10% fall in mean arterial pressure (MAP), which tended to last longer in aged rats. Decreases in heart rate (HR) observed following NPY administration into the NTS were modest but more prolonged than the depressor responses, ANOVA with repeated measures demonstrated no significant effect of age on the MAP or HR response to NPY injection into the NTS. Neuropeptide Y concentrations in the dorsomedial and ventrolateral medulla were not different between the two age groups.

3. Thus, the depressor and bradycardic responses to exogenous NPY administration in the NTS were maintained with age, in keeping with the observation of similar medullary NPY concentrations in adult and aged rats.
BRIEF REVIEW BIOLOGY OF GUT CHOLECYSTOKININ AND GASTRIN RECEPTORS
Authors: Shulkes Arthur , Baldwin Graham S.
Published: June 2007

1. The stomach hormone gastrin and the intestinal hormone cholecystokinin (CCK) share a common C‐terminal pentapep‐tide sequence but have different biological roles. Gastrin is the major stimulant of gastric acid secretion and has a growth stimulatory effect on the secretory part of the stomach. The physiological roles of CCK are the stimulation of pancreatic secretion and the contraction of the gall‐bladder.

2. Several classes of receptors have been defined for peptides of the gastrin/CCK family. The CCKA receptor on pancreatic acini has a greater affinity for sulfated CCK than for gastrin, while the gastrin/CCKB receptor in gastric mucosa and brain has similar affinities for both gastrin and CCK. Potent and selective antagonists have been developed for both receptor classes.

3. The structures of the CCKA and gastrin/CCKB receptors have been deduced from the nucleotide sequences of cloned cDNA. The receptors, which both belong to the family with seven transmembrane segments, control secretion via similar signalling mechanisms. Occupation of either receptor leads to activation of phospholipase C, with resultant increases in intracellular levels of inositol triphosphate and Ca2+. Mitogenic signalling pathways are also being defined.

4. Recent studies have questioned the previous assumption that gastrin precursors are inactive. Glycine‐extended gastrin has been shown to stimulate mitogenesis in some cell lines and may also have an autocrine role in the growth of colonic cancers. The receptors involved, which are clearly distinct in binding properties from the CCKA and gastrin/CCKB receptors, have not yet been cloned. Specific antagonists for the novel receptors will be required to define their function in further detail.
ANGIOTENSIN II‐GENERATING SYSTEM IN DOG AND MONKEY OCULAR TISSUES
Authors: Shiota Naotaka , Saegusa Yumiko , Nishimura Kazuo , Miyazaki Mizuo
Published: June 2007

1. Angiotensin II (Angll) is generated locally in several tissues, including ocular tissues. Recently, it has been suggested that in addition to angiotensin‐converting enzyme (ACE), an alternative Angll‐generating enzyme, chymase, is present in the cardiovascular tissues of humans, monkeys and dogs and may be involved in the local production of Angll. The purpose of the present study was to determine whether chymase contributes to Angll generation in dog and monkey ocular tissues and to clarify the intraocular Angll‐generating system.

2. Chymase‐like and ACE activities were measured in dog and monkey ocular tissues, carotid artery, heart and lung. Their mRNA levels were quantified using the competitive reverse transcriptase‐polymerase chain reaction (RT‐PCR) method.

3. Chymase‐like activity was detected in the anterior uveal tract, choroid and sclera in dog eyes, but not in the cornea, lens or fluid phase (vitreous body and aqueous humor). In monkey eyes, chymase‐like activity was detected in the anterior uveal tract and it was higher here than in the heart. Angiotensin‐converting enzyme activity was detected in the anterior uveal tract, choroid, retina, sclera and fluid phase in both dog and monkey eyes. Chymase and ACE mRNA were detected in tissues showing enzymatic activity.

4. These findings show for the first time that chymase, in addition to ACE, is expressed locally in dog and monkey ocular tissues and may be involved in local Angll generation in the eye.
IS ATHEROSCLEROSIS EXCLUSIVELY A POSTPRANDIAL PHENOMENON?
Authors: Mamo John CL , Yu Kenneth CW , Elsegood Caryn L. , Smith Darrin , Vine Donna , Gennat Hanni C. , Voevodin Melanie , Proctor Spencer D.
Published: June 2007

1. Atherosclerosis begins with the deposition of cholesterol in arterial tissue that is thought to be derived from circulating lipoproteins. There is considerable evidence implicating low density lipoprotein (LDL) as a primary source of plaque cholesterol and, consequently, there are many articles that deal with various aspects of LDL metabolism.

2. Postprandial lipoproteins (i.e. chylomicrons transporting dietary fats) are also considered pro‐atherogenic; however, it is less clear whether their involvement in arterial cholesterol deposition is direct or follows modulation of LDL metabolism.

3. In order to provoke discussion, this article is presented in a manner that suggests atherosclerosis to be exclusively a postprandial phenomenon; that is, we have raised the possibility that LDL is non‐atherogenic.
ROLE OF NITRIC OXIDE IN TUBULOGLOMERULAR FEEDBACK: EFFECTS OF DIETARY SALT
Authors: Welch William J. , Wilcox Christopher S.
Published: June 2007

1. The tubuloglomerular feedback (TGF) response operates primarily by vasoconstriction of the afferent arteriole and a fall in glomerular capillary pressure (PGC) and single‐nephron glomerular nitration rate (SNGFR) during increased NaCl reabsorption in the macula densa (MD). Numerous studies have suggested that nitric oxide (NO) is synthesized by the MD and acts to suppress TGF. As a high‐salt (HS) diet has been found to blunt TGF, we tested the effects of salt intake on NO‐dependent changes in TGF.

2. In the first series of experiments, values of SNGFR were contrasted from samples of tubular fluid taken from the proximal tubule (PT; MD delivery interrupted) and the distal tubule (DT; MD delivery intact). Compared with HS rats, the difference between PT and DT values of SNGFR was increased in low‐salt (LS) diet rats (4.3 ± 0.4 vs 10.3 ± 1.2 nL/min, respectively; P < 0.001). Intravenous infusion of iVG‐monomethyl‐L‐arginine (L‐NMMA), in pressor doses increased the difference between PT and DT values of SNGFR of HS rats (4.3 ± 0.4 vs 9.5 ± 1.2 nL/min before and during L‐NMMA, respectively; P < 0.001) without significantly affecting values in LS rats (10.3 ± 1.2 vs 12.3 ± 1.4 nL/min before and during L‐NMMA, respectively; NS).

3. A second series of experiments assessed TGF responses directly. Changes in stop‐flow pressure (PSF; an index of PGC) were measured in response to graded perfusion of the loop of Henle (LH) with artificial tubular fluid. Loop perfusion with 10‐3 mol/1. L‐NMMA did not affect the PSF responses of LS rats but did reduce (P < 0.01) the PSF of HS rats during perfusion at 20 nL/min (‐1.5±0.4mmHg; P<0.01), 30nL/min (‐1.8 ± O.5 mmHg; P < 0.01) and 40 nL/min (‐2.2 ± 0.5 mmHg; P < 0.001).

4. We conclude that the TGF response is increased by suppression of NOS activity during HS but not LS intake.
ROLE OF NITRIC OXIDE IN THE CONTROL OF THE RENAL MEDULLARY CIRCULATION
Authors: Mattson David L. , Lu Shanhong , Jr Allen W Cowley
Published: June 2007

1. Nitric oxide (NO) has been implicated as an important controller in the short‐ and long‐term regulation of arterial pressure. Studies performed in our laboratory have demonstrated that chronic intravenous administration of the NO synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME) selectively decreases renal medullary blood flow, causes sodium and water retention and leads to hypertension.

2. To determine the importance of the renal medullary effects in this model of hypertension, further studies were conducted to examine the influence of selective stimulation or inhibition of renal medullary NO on whole kidney function and cardiovascular homeostasis. With the use of a unique catheter to directly infuse into the renal medullary interstitial space, stimulation (bradykinin or acetylcholine) or inhibition (L‐NAME) of renal medullary NO selectively increased or decreased renal medullary blood flow.

3. The changes in medullary flow in these experiments were associated with parallel changes in sodium and water excretion independent of alterations in renal cortical blood flow or glomerular filtration rate.

4. Studies were then undertaken to examine the long‐term effects of selective NO inhibition in the renal medulla on cardiovascular homeostasis. Chronic infusion of L‐NAME directly into the renal medullary interstitial space of uninephrectomized Sprague‐Dawley rats led to a selective decrease in renal medullary blood flow that was sustained throughout the 5 day L‐NAME infusion period. The decrease in medullary blood flow was associated with retention of sodium and the development of hypertension and the effects were reversible.

5. The data reviewed indicate that NO in the renal medulla has a powerful influence on fluid and electrolyte homeostasis and the control of blood pressure.
NITRIC OXIDE IN THE MEDIATION OF PRESSURE NATRIURESIS
Authors: Majid DSA , Navar LG
Published: June 2007

1. Recent studies have indicated that nitric oxide (NO) production in the kidney contributes to the regulation of renal haemodynamics and excretory function. Inhibition of nitric oxide synthase (NOS) reduces renal blood flow by approximately 25% and markedly reduces sodium excretion without reductions in filtered load. In particular, inhibition of NO synthesis markedly suppresses the slope of the arterial pressure‐mediated response in sodium excretion.

2. Further studies have shown that constant intrarenal infusion of a NO donor in dogs treated with a NOS inhibitor produced diuretic and natriuretic responses but failed to restore the slope of the pressure‐induced natriuretic response. These data indicate that an alteration in intrarenal NO activity, rather than the simple presence of NO during changes in arterial pressure is required for full expression of pressure natriuretic responses.

3. In support of the hypothesis that NO is involved in the mediation of pressure natriuresis, we also recently demonstrated a direct relationship between changes in arterial pressure and urinary excretion rate of sodium as well as nitrate and nitrite (a marker for endogenous NO activity) in the presence of efficient autoregulation of cortical and medullary blood flow.

4. The direct inhibitory actions of NO on tubular sodium reabsorption have also been observed in cultured tubular cells as well as isolated, perfused cortical collecting duct segments.

5. Thus, the collective data suggest that acute changes in arterial pressure induce changes in intrarenal NO production, which may directly alter tubular reabsorptive function to manifest the phenomenon of pressure natriuresis.
NITRIC OXIDE, THE KIDNEY AND HYPERTENSION
Authors: Schnackenberg C. , Patel AR , Kirchner KA , Granger JP
Published: June 2007

1. According to the renal body fluid feedback mechanism for long‐term control, persistent hypertension can only occur as a result of a reduction in renal sodium excretory function or a hypertensive shift in the pressure natriuresis relationship. Although an abnormal relationship between renal perfusion pressure and renal sodium excretion has been identified in every type of hypertension where it has been sought, factors responsible for this effect are still unclear.

2. Nitric oxide (NO) is produced within the kidney and plays an important role in the control of many intrarenal processes that regulate the renal response to changes in perfusion pressure and, thus, help determine systemic vascular volume and blood pressure. Numerous studies have shown that long‐term inhibition of NO synthesis results in a chronic hypertensive shift in renal pressure natriuresis.

3. Recent studies have shown that certain animal models of genetic hypertension and forms of human hypertension areas are associated with a decrease in NO synthesis. Reductions in NO synthesis reduce renal sodium excretory function, not only through direct actions on the renal vasculature, but through modulation of other vasoconstrictor processes and through direct and indirect alterations in tubular sodium transport.

4. The causes and consequences of the disregulation of NO in hypertension and other renal disease processes remain an important area of investigation.
G02 AND Gi3 PROTEINS MEDIATE THE ACTION OF SOMATOSTATIN ON MEMBRANE Ca2+ AND K+ CURRENTS IN OVINE PITUITARY SOMATOTROPHS
Authors: Chen Chen
Published: June 2007

1. Growth hormone (GH) secretion from the anterior pituitary gland is mainly regulated by hypothalamic GH‐releasing hormone (GHRH) and somatostatin (SRIF). Somatostatin reduces both spontaneous and GHRH‐stimulated GH secretion.

2. Exocytosis of GH is mainly determined by the intracellular free Ca2+ concentration ([Ca2+]i), which is regulated by the influx of Ca2+ via membrane Ca2+ channels. Somatostatin reduces the influx of Ca2+ through two separate mechanisms, namely a direct action on Ca2+ channels and an indirect action on membrane potentials through the activation of K+ channels.

3. In the present experiments, somatotroph‐enriched cells were obtained from the ovine pituitary gland by means of collagenase dissociation and Percoll‐gradient centrifugation. Further identification was based on the effect of SRIF (10 nmol/L) on Ca2+ or K+ currents.

4. A significant reduction in Ca2+ currents and an increase in K+ currents was obtained in response to local application of SRIF (10 nmol/L), but vehicle application had no effect. The responses of Ca2+ and K+ currents to SRIF were reversible after removal of SRIF.

5. Dialysis of GTP‐λ‐s (200 μmol/L) abolished the recovery phase of K+ current response to SRIF after its removal, whereas GDP‐β‐s (200 μmol/L) totally blocked the response. Pretreatment of the cells with pertussis toxin (100 nmol/L) overnight abolished the Ca2+ current response to SRIF.

6. Intracellular dialysis of antibodies to αo, α1_3, ai1‐2 and ai3summits of the G‐proteins into cells via whole‐cell patch‐clamp pipettes was confirmed by immunofluorescent staining of the antibodies.

7. Dialysis of anti‐ai1‐3 or anti‐@aLi3 antibodies significantly attenuated the increase in the K+ current in response to 10 nmol/L SRIF, whereas neither anti‐αo nor anti‐αi_2 antibodies diminished the effect of SRIF on the K+ current.

8. Dialysis of anti‐αo antibodies significantly attenuated the reduction in the Ca2+ current that was obtained upon application of 10 nmol/L SRIF. Neither anti‐αi‐2 nor anti‐αi3 antibody dialysis diminished the effect of SRIF on the Ca2+ current.

9. Dialysis of the ao common antisense oligonucleotides (ASm) but not the αi3 AS significantly diminished the inhibitory effect of SRIF on the Ca2+ current. This effect of ao ASm dialysis occurred at 12 h incubation after dialysis, reaching a maximal level at 48 h and partially recovering at 72 h incubation. Antisense oligonucleotides specific for αo1 (αo1 AS) or αo2(α02 AS) were dialysed into somatotrophs and only αo2 AS significantly attenuated the inhibition of SRIF on the Ca2+ current.

10. It is concluded that the Gi3 protein mediates the effect of SRIF on the K+ current and that the G02 protein mediates the effect of SRIF on the Ca2+ current in primary cultured ovine somatotrophs.
EFFECTS OF INDOMETHACIN ON EPIDERMAL GROWTH FACTOR‐INDUCED RENAL RESPONSES IN SHEEP
Authors: Gow Christine B. , Grant Sharon L. , Phillips Paddy A.
Published: June 2007

1. The effects of indomethacin (an inhibitor of prostaglandin synthesis) on the renal responses to epidermal growth factor (EGF) were investigated in conscious sheep.

2. Ewes (n = 5 per group) received an i.v. saline infusion (150 mL/day) for days 1‐8, followed by either vehicle control, 15 μg/h EGF, 2mg/kg per day indomethacin or 15 μg/h EGF with 2 mg/kg per day indomethacin in 150 mL/day saline, i.v., over days 9‐12. All ewes subsequently received an i.v. saline infusion (150 mL/day) over days 13‐20.

3. Polydipsia, diuresis, transient natriuresis and reduced urine osmolality occurred during EGF treatment alone. There was no effect of EGF on fluid balance, plasma electrolyte or hormone concentrations, plasma osmolality or haematocrit or on the urinary excretion of potassium.

4. Simultaneous infusion of indomethacin with EGF attenuated (P>0.05) the stimulatory effects of EGF infusion alone on urine volume, water intake, natriuresis and urine osmolality.

5. We conclude that prostaglandins may be involved in the diuretic/natriuretic effects of EGF, but may not be the sole mechanism involved.
LOSARTAN AND CAPTOPRIL FOLLOW DIFFERENT MECHANISMS TO DECREASE PRESSOR RESPONSES IN THE PITHED RAT
Authors: Yokoyama Hitomi , Minatoguchi Shinya , Koshiji Masatoshi , Uno Yoshihiro , Kakami Masao , Nagata Chisato , Ito Hiroyasu , Fujiwara Hisayoshi
Published: June 2007

1. We investigated the effects of losartan and captopril on noradrenaline (NA) release and vascular reactivity to NA in the pithed rat.

2. The pressor responses to sympathetic nerve stimulation (SNS) before and after i.v. administration of captopril (1 mg/kg), losartan (1 and 10 mg/kg), sodium nitroprusside (SNP; 5 μg/kg per min), losartan (1 mg/kg) + captopril (1 mg/kg), captopril (1 mg/kg) + losartan (1 mg/kg) or the bradykinin B2 receptor antagonist HOE 140 (1 mg/kg) + captopril (1 mg/kg) were measured. Plasma NA concentrations were measured during 60 s SNS before and after losartan (1 mg/kg), captopril (1 mg/kg), SNP (5 μg/kg per min) or HOE 140 (1 mg/kg) + captopril (1 mg/kg). Pressor responses to exogenous NA were measured before and after administration of losartan (1 mg/kg), captopril (1 mg/kg), HOE 140 (1 mg/kg) + captopril (1 mg/kg) or the nitric oxide synthase (NO) inhibitor, NG‐nitro‐L‐arginine methyl ester (L‐NAME; 10 mg/kg) + captopril (1 mg/kg).

3. Captopril, losartan and SNP decreased frequency‐response curves to a similar extent. The captopril‐induced decrease in pressor responses to SNS was restored by pretreatment with HOE 140. Adding captopril to losartan decreased the curve more than did adding losartan to captopril. Both losartan, captopril and HOE 140 + captopril significantly decreased the plasma NA concentration after SNS (34.1±5.0, 27.4±2.6 and 41.4+8.1%, respectively). Sodium nitroprusside did not change the plasma NA concentration after SNS (3.8±28.2%). The dose‐response curves to i.v. NA were not affected by losartan, but were significantly decreased by captopril. However, responses to NA that were reduced by captopril were restored to control values by pretreatment with HOE 140 or L‐NAME.

4. We suggest that both losartan and captopril decrease pressor responses to SNS by inhibiting NA release from sympathetic nerve endings; however, captopril also decreases ‘vascular reactivity’ to NA, which is mediated by nitric oxide produced by activation of the bradykinin B2 receptors.
HISTOLOGICAL EVALUATION OF CONNECTIVE TISSUE COMPONENTS IN THE HEALING PROCESS OF HUMAN GASTRIC ULCER
Authors: Miyata Akihiro , Goto Hidemi , Niwa Yasumasa , Hayakawa Tetsuo , Nagasaka Tetsuro , Nakashima Nobuo
Published: June 2007

1. The aim of the present study was the evaluation of human gastric ulcer healing and intractability from the viewpoint of connective tissue components.

2. Based on investigations of clinical status, we divided 78 patients with a gastric ulcer into three groups. All patients underwent gastrectomy and group I consisted of 17 patients operated on for bleeding or perforation, group II consisted of 37 patients operated on for an accompanying gastric carcinoma and group III consisted of 24 patients operated on for ulcer intractability.

3. We evaluated, in resected specimens, angiogenesis by Azan‐Mallory staining and fibroplasia by applying proliferating cell nuclear antigen (PCNA) immunostaining. The inflammatory grade and fibrosis at the ulcer base were also evaluated by haematoxylin‐eosin and Azan‐Mallory staining.

4. Microvessel counts in group III were significantly lower than those in groups I and II (P<.05). The PCNA labelling index of fibroblasts in group III was significantly lower than that in groups I and II (P>0.05). The inflammatory grade was severe and fibrosis was excessive in group III.

5. From these results, it is suggested that the reduced angiogenesis and decline in fibrous cell proliferation are important factors contributing to gastric ulcer intractability.
SHORT COMMUNICATION HYPOTENSIVE EFFECTS OF PEPTIDE T IN CONSCIOUS RATS
Authors: Wen Cheng , Liu Dennis T. , Li Ming , Michaelis Jurgen , Grigg Geoffrey W. , Whitworth Judith A.
Published: June 2007

1. The present study investigated the effects of peptide T on mean arterial blood pressure (MAP) in conscious normotensive Sprague‐Dawley (SD) rats, spontaneously hypertensive rats (SHR) and two‐kidney one‐clip (2K1C) hypertensive rats.

2. Peptide T was infused via the left jugular vein at a rate of 1 mg/kg per h in SD, SHR and 2K1C rats and then at doses of 0.1, 0.25, 0.5,1 and 5 mg/kg per h in SHR, with 0.9% saline as a sham control in SHR and 2K1C. Mean arterial pressure was measured directly before, during and after infusion.

3. Peptide T (1 mg/kg per h) decreased blood pressure in both SHR (/><0.01) and 2K1C (P<0.05). In normotensive SD rats the fall in MAP approached statistical significance (P = 0.06). The effect of peptide T was not significantly different in normotensive compared with hypertensive rats. Saline infusion had no effect. The blood pressure lowering effect of peptide T appeared to be dose‐dependent in SHR.