bluuebunny/crossref_metadata_2025 huggingface dataset:
HIGH‐LEVEL EXPRESSION OF RAT D1A DOPAMINE RECEPTOR cDNA IN MOUSE FIBROBLAST LTK‐ CELLS BY n‐BUTYRATE
Authors: Horiuchi Akira , Felder Robin A.
Published: June 2007

1. In order to develop a simple, efficient system for the high‐level expression of dopamine receptors in eukaryotic cells, we have studied the effects of n‐butyrate on the expression of rat D1A dopamine receptor cDNA in mouse fibroblast LTK‐ cells as compared with those of n‐butyrate on endogenous D1 receptor levels in opossum kidney cells.

2. In the transfected LTK‐ cell membranes with pRc/CMV‐D1A receptor cDNA, a selective D1 dopamine antagonist, [3H]‐SCH 23390, exhibited a K4 of 0.9 ± 0.1 nmol/L and a Bmax of 0.35 ± 0.05 pmol/mg protein (n= 5).

3. Addition of n‐butyrate (2–10 mmol/L) to the culture medium for 48 h dose‐dependently increased the D1A receptor level up to 1.5 ± 0.3 pmol/mg protein (n= 7), although the K4 values were not affected. The increase in receptor level was accompanied by an elevation of selective D1 agonist‐induced adenylyl cyclase activity.

4. In contrast, n‐butyrate treatment (2–10 mmol/L) did not affect either endogenous D1 receptor levels or fendoldopam‐induced adenylyl cyclase activity in opossum kidney cells.

5. These results suggest n‐butyrate is a useful tool for obtaining high‐level expression of D1A dopamine receptor cDNA in mouse fibroblast LTK‐ cells.
FOREBRAIN PATHWAYS MEDIATING STRESS‐INDUCED RENIN SECRETION
Authors: Van de Kar Louis D.
Published: June 2007

1. All stressors tested so far increase plasma renin levels; among these are exposure to foot‐shock, immobilization, forced swimming, head‐up tilt, exercise, hypotension haemorrhage and conditioned fear.

2. In old rats (22 months old), conditioned fear stress fails to increase plasma renin concentrations to the same level as in young rats (7 months old).

3. Destruction of cells in the paraventricular hypothalamic nucleus (PVH), either electrolytically or with the cell‐selective neurotoxin ibotenic acid, prevents the effect of conditioned fear stress, but not of immobilization, on plasma renin concentration.

4. Ibotenic acid‐induced lesions in the central amygdaloid nucleus inhibit conditioned fear stress‐induced increases in plasma renin concentrations, but do not reduce the renin response to immobilization. Lesions in lateral amygdaloid nuclei do not reduce the renin response to stressors.

5. Although lesions in the bed nucleus of the stria terminalis (BNST) reduce the adrenocortical response to conditioned fear stress, they do not reduce the effect of stress on plasma renin concentration.

6. Destruction of catecholaminergic terminals in the PVH prevents the effect of conditioned fear stress on plasma renin concentration.

7. Electrolytic lesions in the dorsal raphe nucleus, which is a major site of origin of ascending serotonergic pathways, also inhibit the effect of conditioned fear stress on plasma renin concentration.

8. Activation of serotonin1A (5HT1A) receptors with the anti‐anxiety drugs buspirone and ipsapirone reduces the firing rate of serotonergic neurons in the dorsal raphe nucleus in the midbrain and decreases the effect of stress on plasma renin concentrations. In contrast, the benzodiazepine anxiolytic drugs, chlordiazepoxide and midazolam, are ineffective in inhibiting the renin response to stress.

9. Chemical sympathectomy combined with adrenal medullectomy does not prevent the effect of conditioned fear stress on plasma renin concentration, suggesting that the sympathetic system is not the sole mediator of the message from the brain to the kidneys.

10. Combined, these observations suggest that aversive information from the cortex is transmitted via the amygdala to catecholaminergic cells in the medulla and to serotonergic cells in the dorsal raphe that stimulate the PVH to increase the release of renin.
INTEGRATIVE ROLE OF THE LAMINA TERMINALIS IN THE REGULATION OF CARDIOVASCULAR AND BODY FLUID HOMEOSTASIS
Authors: Johnson Alan Kim , Cunningham J Thomas , Thunhorst Robert L.
Published: June 2007

1. Cardiovascular and body fluid homeostasis depends upon the activation and co‐ordination of reflexes and behavioural responses. In order to accomplish this, the brain receives and processes both neural and chemical input. Once in the brain, information from sources signalling the status of the cardiovascular system and body fluid balance travels, and is integrated, throughout a widely distributed neural network. Recent studies using neuroanatomical and functional techniques have identified several key areas within this neural network. One major processing node is comprised of structures located along the lamina terminalis.

2. Structures associated with the lamina terminalis include the median preoptic nucleus (MePO) and two sensory circumventricular organs (SCVO), the subfornical organ (SFO) and the organum vasculosum of the lamina terminalis (OVLT). Current evidence indicates that blood‐borne signals, such as angiotensin II (AngII), reach SCVO (e.g. SFO) where they are transduced. This information is then carried via neural pathways to brain nuclei (e.g. MePO) where it is integrated with other inputs, such as those derived from systemic arterial blood pressure and volume receptors.

3. Because of their receptive and integrative functions, lamina terminalis structures are essential for the normal control of hormone release (e.g. vasopressin), sympathetic activation and behaviours (thirst and salt appetite), which collectively contribute to maintenance of cardiovascular and body fluid homeostasis.
CARDIOVASCULAR EFFECTS OF ORAL HYPOGLYCAEMIC DRUGS
Authors: Howes Laurence Guy , Sundaresan Purnima , Lykos Denise
Published: June 2007

1. There is increasing evidence that sulfonylurea and biguanide oral hypoglycaemic drugs have cardiovascular effects and influence risk factors for cardiovascular disease in patients with non‐insulin‐dependent diabetes because of actions that are unrelated to alterations in glycaemic control.

2. While sulfonylureas may have anti‐arrhythmic effects following myocardial ischaemia, there is concern that their action on vascular ATP‐sensitive potassium channels may contribute to elevated blood pressure and enhanced vascular responsiveness.

3. In contrast to sulfonylureas, metformin (a biguanide) appears to reduce blood pressure and have beneficial effects on plasma lipoproteins by reducing low‐density lipoprotein cholesterol and possibly increasing high‐density lipoprotein cholesterol levels.

4. The pharmacological basis and clinical significance of these effects of sulfonylureas and biguanides require further investigation.
EFFECTS OF CELERY EXTRACT AND 3‐N‐BUTYLPHTHALIDE ON LIPID LEVELS IN GENETICALLY HYPERCHOLESTEROLAEMIC (RICO) RATS
Authors: Tsi D. , Tan BKH
Published: June 2007

1. Aqueous celery extract was administered intraperitoneally to genetically hypercholesterolaemic (RICO) and normochol‐esterolaemic (RAIF) rats via Alzet osmotic pumps over a 13 day period.

2. The serum cholesterol concentration of the celery extract‐treated RICO rats was found to be significantly lower (P<0.05) than the control rats. Aqueous celery extract was effective in preventing the rise of cholesterol level in the RICO rats. However, no such observation was seen in the RAIF rats. The serum triglyceride level was unchanged in both strains of rats.

3. When 3‐n‐butylphthalide (BuPh), a unique component in celery, was administered in the same manner to the RICO and RAIF rats, it did not produce significant changes in the serum and liver lipid profiles of these rats. The activities of hepatic 3‐hydroxy‐3‐methylglutaryl CoA reductase in both strains of rats were also not significantly different from their respective controls.

4. Together with our recently reported thin‐layer chroma‐tography findings that BuPh was not detected in the aqueous celery extract, this study suggests that the effect of celery extract on serum cholesterol levels in the RICO rats could be attributed to chemical constituents other than BuPh.
RELATIONSHIP BETWEEN NIFEDIPINE SENSITIVITY OF AORTAE AND BLOOD PRESSURE OF STROKE‐PRONE SPONTANEOUSLY HYPERTENSIVE RATS
Authors: Jiang Guang‐Chi , Iwanov Victor , Moulds Robert FW
Published: June 2007

1. We have previously described an increased sensitivity to inhibition by nifedipine of noradrenaline‐induced contractures of blood vessels in hypertension. In this study we have investigated whether changes in blood pressure (BP) change the sensitivity to nifedipine and K+ of aortic rings from normotensive (Wistar‐Kyoto rats, WKY) and stroke‐prone spontaneously hypertensive rats (SHRSP).

2. SHRSP were treated with: hydralazine plus hydrochloro‐thiazide; captopril plus hydrochlorothiazide; hydralazine plus guanethidine; or captopril alone. WKY rats were treated with deoxycorticosterone acetate (DOCA) and NaCl. Treatment commenced from 5 weeks of age and continued until 13–15 weeks.

3. The SHRSP treatments produced similar reductions in BP, and the BP of all the treated groups were significantly lower than the mean BP of untreated SHRSP (201.0 ± 7.7 mmHg). The mean BP of the treated WKY rats (134.2 ± 7.6 mmHg) was significantly higher than the mean BP of the untreated WKY rats (86.8 ± 7.4 mmHg).

4. An area‐under‐curve (AUC) analysis of the inhibitory effects of nifedipine on responses of aortae to noradrenaline showed no differences between treated and untreated SHRSP groups (overall mean 40.6 ± 1.9% and 43.4 ± 3.4% inhibition of control AUC, respectively), or between DOCA‐salt treated WKY and untreated WKY groups (58.8 ± 5.9 and 64.8 ± 2.3, respectively). Noradrenaline‐induced contractures of aortae from all SHRSP groups were significantly more sensitive to inhibition by nifedipine than aortae from both WKY groups.

5. The molar concentration of agonist required to evoke 50% of the maximum response (EC50) values for potassium chloride (KCI) were significantly increased in the aortae of all treated SHRSP groups in comparison to those from untreated SHRSP (treated SHRSP groups, 15.53 ± 0.68 mmol/L vs untreated SHRSP group, 11.36 ± 1.10 mmol/L). The EC50 values for KC1 for the aortae from the DOCA‐treated WKY rats were significantly less than those from aortae of the untreated WKY (11.80 ± 0.80 and 17.08 ± 1.50 mmol/L, respectively).

6. We conclude that reduction (in SHRSP) or increase (in WKY) of the BP has no effect on the sensitivity of aortic smooth muscle to the inhibitory effects of nifedipine on responses to noradrenaline, suggesting that alterations in voltage‐dependent Ca2+ mechanisms may be a primary phenomenon in the SHRSP. In contrast, the fact that sensitivity to KC1 changes in the treated SHRSP and WKY aortae suggests such sensitivity is secondary to the BP and thus a separate phenomenon from voltage‐dependent Ca2+ mechanisms.
GENDER DIFFERENCES IN RESPONSE TO ENDOTHELIN‐1 IN CORONARY ARTERIES: TRANSCRIPTION, RECEPTORS AND CALCIUM REGULATION
Authors: Miller Virginia M. , Barber Dustan A. , Fenton Alexis M. , Wang Xiaofang , Sieck Gary C.
Published: June 2007

1. Experiments were designed to determine how sex hormonal status may influence production and response to endothelins.

2. Circulating concentrations of endothelin‐1 were not different between sexually mature male and female pigs and did not differ between females of low‐ and high‐oestrogen status.

3. Expression of messenger RNA for preproendothelin was not different in aortic endothelial cells derived from sexually mature male and female pigs.

4. Endothelin‐1, endothelin‐3 and sarafotoxin S6c caused concentration‐dependent contractions of rings of coronary arteries suspended for the measurement of isometric force. Only in response to endothelin‐1 were contractions greater in arteries from female than in male pigs. This difference was not related to oestrogen levels in females.

5. The intrinsic force‐calcium relationship defined in smooth muscle cells permeabilized with either triton‐X or β‐escine was not different in coronary arteries from male and female pigs. The calcium sensitivity was increased to the same extent by endothelin‐1 in smooth muscle from male and female pigs.

6. Competitive inhibition of radiolabelled endothelin‐1 by unlabelled endothelin‐1 was not different in membranes prepared from coronary arteries from male and female pigs. However, competitive inhibition of radiolabelled endothelin‐1 by unlabelled endothelin‐3 showed two binding sites. The affinity of the high affinity binding site was increased only in females with high oestrogen levels.

7. These results suggest that there are gender differences in contractions of porcine coronary arteries to endothelin‐1. These differences may not relate to transcriptional regulation for the production of the peptide in endothelial cells, to the regulation of the number or affinity of endothelin receptors or to intrinsic calcium‐sensitivity of the contractile proteins. Rather they are probably due to differences in the regulation of intracellular calcium.
ACTION OF CHOLINESTERS ON SENSORY NERVE ENDINGS IN SKIN AND MUSCLE
Authors: Carr RW , Proske U.
Published: June 2007

1. This is a review of the literature on the subject of the effects of cholinesters and their agonists on sensory nerve endings.

2. The present‐day view is that acetylcholine (ACh) has an excitatory action on some cutaneous receptors. Responses appear to be limited to receptors served by small myelinated and un‐myelinated axons where responsiveness is multimodal; that is, the receptors are activated by noxious thermal and mechanical stimulation.

3. The possible role played by acetylcholine in sensory transduction processes is discussed, as are other explanations for the presence of nicotinic cholinergic receptors on the terminals of cutaneous receptors.

4. The excitatory action of ACh and succinylcholine (SCh) on muscle spindles is described. Two possible mechanisms are considered: a direct depolarizing action on the nerve terminals and indirect excitation, brought about by a contracture of the intrafusal fibres on which the sensory endings lie.

5. The technique of using SCh in combination with fusimotor stimulation is described. This has provided new information about the internal workings of muscle spindles. Brief mention is also made of the action of SCh on tendon organs and joint receptors.

6. It is concluded that a direct action by cholinesters is restricted to receptors served by small axons with multimodal functions. The precise role of such an action remains the subject of speculation. Possible clinical significance is discussed.
EFFECT OF 8‐SULFOPHENYL THEOPHYLLINE ON ENDOGENOUS NORADRENALINE RELEASE FROM SYMPATHETIC NERVES OF THE RABBIT EAR ARTERY
Authors: Ishii Reiko , Shinozuka Kazumasa , Kunitomo Masaru , Hashimoto Takao , Takeuchi Koichi
Published: June 2007

1. The release of endogenous noradrenaline (NA) and adenyl purine (ATP, ADP, AMP and adenosine) from the rabbit ear artery, evoked by electrical stimulation (ES; 16Hz), was examined.

2. ES evoked a significant release of NA and adenyl purine; the ratio of the amount of total purine released to NA released was approximately 180 on a molar base.

3. ES‐evoked purine release was significantly reduced by the denudation of the endothelium and abolished by the α1‐adrenoceptor antagonist, prazosin (1 μmol/L).

4. ES‐evoked NA release was significantly reduced by a P1‐purinoceptor antagonist, 8‐sulfophenyl theophylline (8SPT). Purine release was slightly reduced by 8SPT.

5. These results suggest that endogenous NA released by ES results in the release of a large amount of purine, which may, in turn, increase the release of NA by acting on prejunctional purinoceptors on sympathetic nerve terminals.
DEHYDROEPIANDROSTERONE DOES NOT PREVENT ADRENOCORTICOTROPHIN‐INDUCED HYPERTENSION IN CONSCIOUS RATS
Authors: Li Ming , Wen Cheng , Martin Allison , Whitworth Judith A
Published: June 2007

1. We tested the hypothesis that dehydroepiandrosterone (DHEA), which prevents dexamethasone‐induced hypertension in rats, may block adrenocorticotrophin (ACTH) hypertension, which has been presumed due to corticosterone excess. The blood pressure and metabolic effects of DHEA (18 mg/kg per day) were examined in sham and ACTH‐treated (0.5 mg/kg per day) conscious Sprague‐Dawley rats (n= 20).

2. ACTH but not sham injection increased blood pressure, water intake and urine output and decreased bodyweight.

3. DHEA administration for 10 days did not alter blood pressure or metabolic effects in either sham or ACTH‐treated rats.

4. DHEA, which is known to block dexamethasone‐induced hypertension, did not modify ACTH‐induced hypertension in the rat. This suggests either that ACTH‐induced hypertension is not simply a consequence of glucocorticoid activity or that the action of DHEA in dexamethasone hypertension is not through blocking the glucocorticoid receptor.
DOSE DEPENDENT IN VIVO INHIBITION OF HUMAN COLORECTAL CANCER (LoVo) BY THE GASTRIN RECEPTOR ANTAGONIST, CI‐988
Authors: Romani Rossana , Howes Laurence G , Morris David L
Published: June 2007

1. The dose‐response relationship of a new, potent and selective cholecystokinin B receptor antagonist, CI‐988, on the growth of LoVo, a human colon cancer cell line, was studied in vivo.

2. We have previously shown the growth of LoVo to be inhibited both in vitro and in vivo by CI‐988.

3. LoVo was grown for 10 days in nude mice that were then treated with CI‐988 at 1,5,10,25 and 50 mg/kg per day orally for 20 days.

4. CI‐988 significantly inhibited the growth of xenografts at all concentrations except the highest concentration of 50 mg/kg per day (P<0.00001; anova). The largest inhibitory activity was caused by the 10 mg/kg per day dose, causing a 47% inhibition at day 29 (P= 0.00003; Newman‐Keul's test).

5. CI‐988 may be of use in inhibiting the growth of colorectal cancer.
CALCITONIN GENE‐RELATED PEPTIDE ANTAGONIZES THE PROTECTIVE EFFECT OF ADRENOMEDULLIN ON HISTAMINE‐INDUCED BRONCHCTION
Authors: Kanazawa Hiroshi , Kawaguchi Takashi , Kamoi Hiroshi , Fujii Tatsuo , Kudoh Shinzoh , Hirata Kazuto , Kurihara Naotsugu , Yoshikawa Junichi
Published: June 2007

1. In the present study the possible relationship between adrenomedullin (AM) and calcitonin gene‐related peptide (CGRP) in the regulation of airway functions in anaesthetized guinea‐pigs was examined in vivo.

2. We found that AM significantly inhibited histamine‐induced bronchoconstriction in a dose‐dependent manner. CGRP or the CGRP receptor antagonist (CGRP [8–37]) alone did not affect pulmonary resistance and pretreatment with CGRP or CGRP [8–37] did not significantly affect histamine‐induced bronchoconstriction. However, AM‐induced broncho‐protection was significantly inhibited by pretreatment with CGRP or CGRP [8–37] in a dose‐dependent manner.

3. It is therefore possible that CGRP may be competitive, at least in part, with binding sites of AM in the guinea‐pig airway. Exogenous AM may be useful for the management of bronchial asthma, not only as a potent bronchodilator, but also as a functional antagonist of CGRP.
RELATIONSHIP BETWEEN ALTERATIONS IN LYMPHOCYTE AND MYOCARDIAL β‐ADRENOCEPTOR DENSITY IN PATIENTS WITH LEFT HEART VALVULAR DISEASE
Authors: Dzimiri Nduna , Moorji Azadali
Published: June 2007

1. We have evaluated the possibility that alterations in lymphocyte β‐adrenoceptor density may be related to changes in the myocardial population in left heart valvular diseases. Receptor density and their binding affinities were estimated using [125I]‐iodocyanopindolol.

2. The lymphocyte (LC) β‐adrenoceptor density was 43.4 ± 5.6 fmol/mg protein in the controls (n= 35) and 81% lower in heart valvular patients (n= 86). In myocardial controls (n= 18), the left ventricular (LV) receptor density was 167.2 ± 29.8 fmol/mg protein, right ventricular (RV) density was 123.1 ± 14.6 fmol/mg, left atrial (LA) density was 81.6 ± 10.5 fmol/mg and right atrial (RA) 108.1 ± 14.5 fmol/mg. Compared with this group, the receptor density of the study patients (n= 47) decreased by 67, 43, 24 and 32% in the LV, RV, LA and RA, respectively. The decrease in LC was twice that of the average total myocardial receptor density.

3. When patients were classified according to their left ventricular load conditions as having either left ventricular pressure overload (LVP), left ventricular volume overload, mixed lesions (MOL) and no left ventricular overload (mitral stenosis; NOL), the attenuation in LC receptor density reached statistical significance for all four groups, without showing significant difference between the individual groups. In contrast, the decrease in all chambers was predominantly due to volume overload. MOL and NOL exerted intermediate effects that were significant in the LV, while LVP did not contribute to the changes in the LA.

4. Accordingly, the reduction in peripheral β‐adrenoceptor density may reflect the extent to which particularly the volume overload exerts its influence on myocardial β‐adrenoceptors in left heart valvular patients.
EXTRACELLULAR ATP INCREASES CYTOSOLIC CALCIUM IN CULTURED RAT RENAL ARTERIAL SMOOTH MUSCLE CELLS
Authors: Inscho Edward W , Belott Todd P , Mason Michael J , Smith Jeffry B , Navar L Gabriel
Published: June 2007

1. Experiments were conducted on cultured renal arterial smooth muscle cells to determine the ability of extracellular ATP to alter cytosolic calcium concentration and to determine the mechanisms by which this effect occurs.

2. ATP (100 μmol/L) caused the fluorescence ratio of fura‐2 to increase from a control value of 1.06±0.05 to 2.06±0.13 (P<0.01) before stabilizing at a sustained level of 1.35±0.04 (n= 8; P<0.05).

3. Removal of extracellular calcium from the bathing medium resulted in an attenuation of the initial response to 100 μmol/L ATP with cell fluorescence increasing from 1.16±0.18 to 1.44±0.18 ratio units (n= 5). Furthermore, the initial increase in fluorescence ratio rapidly declined to 1.02±0.06, indicating that an influx of extracellular calcium is required to sustain the increase in fura‐2 fluorescence.

4. Depletion of intracellular calcium pools with thapsigargin prevented the increase in fura‐2 fluorescence evoked by ATP.

5. These data suggest that ATP‐mediated increases in cytosolic calcium in cultured renal arterial smooth muscle cells involve calcium release from the thapsigargin‐sensitive, intracellular pool in conjunction with calcium influx from the extracellular medium.
CELLULAR LOCALIZATION OF ENDOTHELIN RECEPTOR SUBTYPES IN THE RAT KIDNEY FOLLOWING IN VITRO LABELLING
Authors: Dean Rachael , Zhuo Jialong , Alcorn Daine , Casley David , Mendelsohn Frederick AO
Published: June 2007

1. We have previously shown that [125I]‐endothelin (ET) receptor binding is localized almost exclusively to the fenestrated endothelial cells of glomerular capillaries and peritubular capillaries in the rat kidney following systemic administration of the radioligand in vivo. Because of the lack of specific ET receptor binding in other glomerular and tubular structures following in vivo labelling, we undertook further studies, using electron microscopic autoradiography and ET receptor subtype selective ligands, to investigate whether other renal components also contain ET receptor binding and, if so, to determine the cellular localization of the ET receptor subtypes, ETA and ETB, following in vitro labelling.

2. At the electron microscopic level, ET binding sites were localized primarily to the fenestrated endothelium of glomerular and peritubular capillaries of the cortex, inner stripe of the outer medulla and the inner medulla. ET binding sites also occurred overlying renomedullary interstitial cells (RMIC) of the inner medulla.

3. The ETB receptor selective agonist, sarafotoxin 6c (S6c), abolished ET binding in the vascular endothelium throughout the kidney, while the ETA receptor selective antagonist, BQ123, was without effect. Both BQ123 and S6c partially inhibited the binding in the RMIC of the inner medulla.

4. These results indicate that ET receptor binding in the fenestrated endothelium in the glomerular capillaries and peritubular capillaries belongs mainly to the ETB subtype, whereas both ETA and ETB subtypes are present in the RMIC.
EFFECTS OF ANAESTHETICS AND TRAUMA ON STIMULATED GASTRIC ACID SECRETION IN CHRONIC FISTULA DOGS
Authors: Bastaki SMA , Waton NG
Published: June 2007

1. The present study was undertaken to determine whether various anaesthetic agents affect canine gastric acid secretion independently of other experimental variables.

2. Acid secretory output was determined in dogs with chronic fistulae, by administering sedating doses of anaesthetics commonly used for studying gastric secretory mechanisms in laboratory animals.

3. The anaesthetic agents inhibited gastric acid secretion. As the inhibitory effect of the mixture of anaesthetics was pronounced, an attempt was made to study the effect of each individual anaesthetic agent separately.

4. Acetopromazine was given to sedate dogs. Although it has a long duration of action, it only had a transient inhibitory action on gastric acid secretion of 15–30 min duration. Moreover the drug reduced pentagastrin‐stimulated secretion, but had no effect on histamine‐stimulated secretion.

5. Thiopentone sodium given with acetopromazine produced a mild inhibitory effect on histamine‐stimulated secretion for 45 min, but produced a more pronounced and sustained inhibitory effect on pentagastrin‐stimulated secretion.

6. Trilene significantly inhibited both histamine‐ and pentagastrin‐stimulated secretion. The effect on the latter was more pronounced and sustained.

7. Trauma had no significant effect on histamine‐stimulated secretion, but showed a slight inhibitory effect on pentagastrin‐stimulated secretion.

8. Experiments to study gastric secretory mechanisms and antisecretory drugs should take account of the potential inhibitory effects of anaesthetics. Where possible, studies in conscious dogs with gastric fistulae are preferable to experiments on anaesthetized animals.
ANGIOTENSIN CONVERTING ENZYME INHIBITION IN THE POSTNATAL RAT RESULTS IN DECREASED CELL PROLIFERATION IN THE RENAL OUTER MEDULLA
Authors: McCausland Jane E , Ryan Graeme B , Alcorn Daine
Published: June 2007

1. Chronic angiotensin converting enzyme (ACE) inhibition or AT1 antagonism during postnatal development in the rat has been shown to cause renal tubular and vascular damage, particularly in the outer medulla.

2. The effects of ACE inhibition were investigated at a stage of development before the renal outer medulla is fully established.

3. Sprague‐Dawley rat pups were given daily i.p. injections of either enalapril or saline from days 3–10. At day 11, kidneys were perfusion‐fixed for either electron microscopy or immunocytochemistry. Sections were incubated in proliferating cell nuclear antigen (PCNA) antisera and the avidin‐biotin immunoperoxidase method was used to detect an immunoreactive product, indicative of proliferating cells.

4. Following enalapril treatment, the normal structural arrangement of the outer medulla was disrupted compared with controls. Cell proliferation (PCNA‐positive cells) in the medullary rays was reduced in enalapril‐treated kidneys compared with control kidneys.

5. Thus, angiotensin II appears to be essential for normal tubular and vascular growth in postnatal renal development in the rat.
EFFECTS OF ANTIHYPERTENSIVE DRUGS ON CORONARY ARTERY DISEASE RISK: A META‐ANALYSIS
Authors: Howes LG , Lykos D. , Rennie GC
Published: June 2007

1. The effects of antihypertensive drugs on lipids may also influence their effect on coronary artery disease (CAD). However, the clinical significance of these effects and the extent to which they persist during long‐term therapy is uncertain.

2. We performed a meta‐analysis on 23 randomized trials published between 1988 and 1994 that compared the effects of atenolol, celiprolol (a β‐blocker with β2‐adrenoceptor intrinsic sympathomimetic activity), enalapril, nifedipine and doxazosin on plasma cholesterol, low density lipoprotein cholesterol (LDL‐C), high density lipoprotein cholesterol (HDL‐C), triglycerides and blood pressure (BP).

3. Predicted changes in CAD risk were calculated by incorporating the results for these parameters into the Framingham equations.

4. While there were no differences in antihypertensive efficacy between the drugs, atenolol significantly (P > 0.05) reduced HDL‐C and increased total cholesterol, LDL‐C and triglycerides compared with celiprolol, enalapril, doxazosin and nifedipine.

5. The magnitude of the effects on lipids was not significantly influenced by the duration of therapy (up to 3 years for atenolol and doxazosin and up to 2 years for celiprolol).

6. The improvement in Framingham equation point scores (systolic BP formula) was significantly (P > 0.05) less for atenolol (− 0.54; confidence intervals (CI) − 0.29–0.78) than for celiprolol (−1.69; CI −0.68 ‐2.70), doxazosin (−1.67; CI −1.11–2.23), enalapril (−1.43; CI 0.23–3.07) and nifedipine (−1.91; CI −1.22–2.59). Similar results were obtained for the Framingham diastolic BP formula.

7. These results suggest that the adverse effects of atenolol on plasma lipids do not improve with prolonged therapy and are theoretically great enough to reduce its efficacy in reducing CAD by approximately two thirds compared with antihypertensive drugs that do not adversely affect plasma lipids. However it must be emphasized that these are theoretical effects. In order to determine the actual differences between these drugs on CAD end points, studies using these end points are required.
PCR‐SSCP ANALYSIS OF THE PROMOTER REGION OF THE RENIN GENE IN PATIENTS WITH ALDOSTERONE‐PRODUCING ADENOMAS
Authors: Ballantine DM , Klemm SA , Tunny TJ , Stowasser M. , Gordon RD
Published: June 2007

Aldosterone‐producing adenomas (APA) of the adrenal gland may be responsive or un‐responsive to the renin‐angiotensin system.

2. We have described increased expression of renin mRNA in angiotensin‐responsive aldosterone‐producing adenomas (AII‐R‐APA) compared with angiotensin‐un‐responsive aldosterone‐producing adenomas (AII‐U‐APA) and significantly different allelic frequencies of the BglI, TaqI and HinfI restriction fragment length polymorphisms of the renin gene between the two groups.

3. An area including the 5’ flanking region—500 bp from exon 1, exon 1 and intron A contained no gross insertions or deletions when studied by a long polymerase chain reaction technique.

4. In the present study, polymerase chain reaction‐single strand conformation polymorphism analysis (PCR‐SSCP) revealed no single base pair alteration in the proximal promoter region (—600 bp to transcription start) of the renin gene in patients with APA (either AII‐U‐APA or AII‐R‐APA) when compared with normal subjects.

5. Therefore, mutations in this regulatory region do not appear to explain the different levels of renin gene expression observed in these two subtypes of APA.
GENETIC VARIANTS OF PROTEINS FROM THE RENIN ANGIOTENSIN SYSTEM ARE ASSOCIATED WITH PRESSURE LOAD CARDIAC HYPERTROPHY
Authors: Wong KK , Summers KM , Burstow DJ , West MJ
Published: June 2007

1. The relationship between the angiotensinogen (AGT) T174M, angiotensin converting enzyme (ACE) insertion/deletion (I/D) and the angiotensin II type 1 receptor (AT1) genetic markers and left ventricular hypertrophy was examined in normal subjects and those with aortic stenosis.

2. Subjects with aortic stenosis had higher left ventricular systolic pressure and relative wall thickness (RWT) compared with normal. However, within aortic stenosis subjects, left ventricular RWT did not correlate with left ventricular systolic pressure or with aortic valve area.

3. In subjects with aortic stenosis, left ventricular RWT was higher in those with ACE DD (P<0.05) or AGT T174M (P<0.06) compared with those with the ACE II or ID genotype or AGT TT174 genotype. No relationship was observed with any of the AT1 alleles. The ACE and AGT genetic markers independently predicted left ventricular RWT in aortic stenosis. No association was observed between these genotypes and left ventricular RWT in normal subjects.

4. The data suggest that the AGT T174M and ACE I/D genotypes may act together to influence the degree of hypertrophy in subjects with aortic stenosis.

5. In patients with aortic stenosis, genetic variants of proteins from the renin angiotensin system may be at least as important as left ventricular systolic pressure in determining the degree of left ventricular hypertrophy and could therefore explain the clinical variation observed in the progression to cardiac dysfunction.
PRODUCTION OF 18‐OXO‐CORTISOL IN SUBTYPES OF PRIMARY ALDOSTERONISM
Authors: Stowasser Michael , Bachmann Anthony W , Tunny Terry J , Gordon Richard D
Published: June 2007

1. In familial hyperaldosteronism type I (FH‐I), expression of an adrenocorticotropic hormone (ACTH)‐dependent hybrid 11β‐hydroxylase/aldosterone synthase gene causes excessive ‘hybrid steroid’ (18‐hydroxy‐ and 18‐oxo‐cortisol) production. In order to study the mechanism of elevated ‘hybrid steroid’ levels in angiotensin‐unresponsive (AII‐U) aldosterone‐producing adenoma (APA), we compared responses of 24 h urinary 18‐oxo‐cortisol, aldosterone and cortisol to dexamethasone (0.5 mg q6h for 4 days) in 11 FH‐I patients, 11 patients with AII‐U APA, 11 patients with AII‐responsive (AII‐R) APA and 10 patients with bilateral adrenal hyperplasia (BAH).

2. Consistent, marked suppression (by at least 60%) of 18‐oxo‐cortisol levels by dexamethasone was seen in all groups except AII‐U APA. Aldosterone levels were consistently suppressed to undetectable levels only in FH‐I. Cortisol levels were suppressed to undetectable levels in all patients except two with AII‐U APA.

3. Production of both 18‐oxo‐cortisol and aldosterone (and occasionally cortisol) in AII‐U APA appears relatively ACTH‐independent, consistent with a common mechanism involved in the formation of these two steroids from their respective precursors, which differs from that in FH‐I.

4. In AII‐R APA and BAH, 18‐oxo‐cortisol production appears markedly ACTH‐dependent, but aldosterone production is not.
α1‐ANTITRYPSIN DEFICIENCY ALLELES AND BLOOD PRESSURE IN AN AUSTRALIAN POPULATION
Authors: Huggard PR , West MJ , Summers KM
Published: June 2007

1. Two deficiency alleles of α1‐antitrypsin (AAT) called S and Z have been previously associated with lower blood pressure levels.

2. A sample of Australian hypertensive and normotensive subjects was investigated with respect to these alleles.

3. No association of blood pressure levels with these AAT alleles was found in our study sample.
NON‐INVASIVE ASSESSMENT OF BAROREFLEX SENSITIVITY AND RELATION TO MEASURES OF HEART RATE VARIABILITY IN MAN
Authors: Pellizzer A‐M , Kamen PW , Jackman G. , Brazzale D. , Krum H.
Published: June 2007

1. We have developed a simple noninvasive method to assess the spontaneous baroreflex (BRS; reflex heart rate response to change in systemic blood pressure) in man. The BRS is impaired in many cardiovascular disorders and is known to be of major prognostic significance; however, the invasive nature of traditional BRS assessment has thus far limited its clinical application.

2. Sixteen healthy subjects (7M, 9F; age 28 ± 3 years) were studied at baseline and during stepwise i.v. infusion of phenylephrine and bolus i.v. dosing of nitroprusside. Invasive BRS was derived from linear regression of the change in systolic blood pressure (SBP) and RR interval from baseline following these perturbations. Noninvasive BRS was derived from approximately 1500 gated beat‐to‐beat SBP and RR interval data points acquired by Finapres BP and continuous ECG monitoring. Slopes were derived from linear regression of three consecutive baroreflex‐mediated data points (following a phase shift of one RR interval from its accompanying SBP value) and were averaged to determine BRS. Correlations between invasive and noninvasive BRS measures were found to be highly significant (r = 0.78; P= 0.0009; slope = 0.87).

3. Significant correlations between noninvasively determined BRS and heart rate variability derived measures of autonomic activity (24h standard deviation of normal RR intervals, root mean square of successive RR intervals, low frequency and high frequency power) were also observed (r = 0.79–0.83; P= 0.003–0.008).

4. These results support the validity of this noninvasive method of measurement of BRS in man and of a parasympathetic contribution to spontaneous baroreflex.
Proceedings of the Symposium ‘Angiotensin AT1 Receptors: From Molecular Physiology to Therapeutics’: HUMAN TYPE‐1 ANGIOTENSIN II (AT1) RECEPTOR GENE STRUCTURE AND FUNCTION
Authors: Curnow Kathleen M
Published: June 2007

The type‐1 angiotensin II (AngII) receptors, designated AT1, mediate most of the biological actions of the peptide hormone AngII. They are the most recent drug target for the treatment of hypertension and cardiac failure and basic research is now focusing on the mechanisms that regulate their expression.

In humans there is a single AT1 gene. It encodes a 47 kb pre‐mRNA containing five exons, with the previously described AT1 open reading frame (ORF) on exon 5. Alternative splicing results in the production of mature mRNA that are translated at different efficiencies and encode two receptor isoforms. The inclusion of exon 2 markedly inhibits translation of the downstream ORF, both in vitro and in vivo. Nonetheless, this exon is present in up to one‐half of AT1 mRNA in all tissues studied.

Transcripts containing exon 3 spliced to exon 5 encode a receptor with an amino‐terminal extension of 32 amino acids and represent up to one‐third of total AT1 mRNA in each tissue examined. In vitro, these latter transcripts are translated to produce a longer receptor and, in transfected cells, they encode a functional AT1 receptor with ligand‐binding and signalling properties similar to those of the short isoform.

Exon 4 is of minor significance as it is rarely spliced into AT1 mRNA.

These data indicate that, in addition to characterizing factors that modulate AT1 promoter activity and RNA stability, it is important to analyse the splicing patterns of this gene when studying the regulation of its expression.
EFFECTS OF ONE‐CLIP, ONE‐KIDNEY HYPERTENSION IN CHRONICALLY CATHETERIZED PREGNANT EWES
Authors: Lumbers ER , Burrell JH , Stevens AD , Weir BA
Published: June 2007

1. Hypertension secondary to renal disease was studied in non‐pregnant and pregnant ewes to determine whether there were any changes in arterial pressure and the distribution of cardiac output and, in particular, whether uteroplacental blood flow was affected.

2. In six non‐pregnant, chronically catheterized, uninephrec‐tomized ewes, a reduction in renal blood flow (RBF) to 40–50% of control caused hypertension within 3 h. This was maintained for as long as RBF was reduced (72 h) and returned to control 24 h after the occluder around the renal artery was released. When this experiment was repeated in 16 uninephrectomized pregnant ewes (118–134 days gestation) hypertension occurred within 3 h and was sustained for as long as RBF was reduced (between 24 and 72 h). Arterial pressure returned to control within 24–72 h of restoring RBF.

3. Compared with non‐pregnant ewes, pregnant ewes had similar arterial pressures, higher cardiac outputs (CO; P < 0.001) and heart rates (HR; P < 0.001), lower total peripheral resistances (TPR; P < 0.001) and similar blood flows to brain, ovary, pancreas, kidney and spleen. Splenic vascular resistance (VR) was greater (P= 0.006), gut blood flow was greater (P < 0.05) and gut VR was less (P < 0.05). Myoendometrial blood flow/g was greater (P < 0.005) and myoendometrial VR was less (P= 0.006).

4. In pregnant sheep with renal clip hypertension, there was no change in CO and HR, but TPR increased (P < 0.01), as did plasma renin activity. Gut, brain, pancreatic and myoendometrial VR were increased as long as RBF was reduced; in addition, myoendometrial VR remained high for the rest of the experiment. Placental blood flow was unchanged at 3h; 24–72 h later it was reduced (P < 0.05) and remained low. Placental VR was increased 24–72 h after RBF was restored when ewes were again normotensive.

5. Thus, one‐clip, one‐kidney renal hypertension in the pregnant ewe was due to increased TPR associated with a fall in uteroplacental blood flow that persisted even when RBF was restored and ewes were normotensive. This reduction in uteroplacental blood flow could account for the high foetal morbidity and mortality that occurs in pregnant women with renovascular hypertension.
RENIN, PRORENIN, AND RENIN GENE EXPRESSION IN RATS WITH ACUTE NEPHROTIC SYNDROME
Authors: Ibarra‐Rubio Maria Elena , V Margarita Ramos , Correa‐Rotter Ricardo , Pedraza‐Chaverri Jose
Published: June 2007

1. The concentration of total, active and inactive renin was analysed in plasma, urine and kidney from control (C), pair‐fed (PF) and nephrotic (NS) rats, as well as renin mRNA levels in kidney, liver and brain.

2. Nephrotic syndrome were induced by a single subcutaneous injection of puromycin aminonucleoside (PAN) and determinations were made 6 days after PAN injection.

3. Plasma total renin did not change, active renin increased in NS rats with respect to PF and C groups and in PF rats with respect to C. In contrast, the inactive renin percentage decreased in NS rats with respect to PF and C groups and in PF animals with respect to C. Total, active and inactive renal renin content did not change and active and inactive renin were significantly excreted by urine with no changes in the prorenin percentage with respect to C and PF groups.

4. In both NS and PF groups, renin mRNA levels did not change in any of the tissues studied. In another group of rats, kidney renin mRNA levels were measured on days 1, 3, 5 and 7 after PAN injection and no time‐course changes in its expression were found.

5. These results suggest that renin gene expression is not altered in acute nephrotic syndrome and that plasma renin concentration is regulated at the translational or post‐translational level in this experimental model.
DIURNAL EFFECTS OF FLUOXETINE AND NALOXONE ON THE HUMAN HYPOTHALAMIC‐PITUITARY‐ADRENAL AXIS
Authors: Torpy DJ , Grice JE , Hockings GI , Walters MM , Crosbie GV , Jackson RV
Published: June 2007

1. Central serotonergic pathways are hypothesized to be involved in the stimulation of hypothalamic adrenocorticotropic hormone (ACTH) secretagogue release by both circadian‐ and stress‐induced mechanisms. We aimed to investigate this hypothesis by measuring the effect of the highly specific serotonin re‐uptake inhibitor fluoxetine (FX) on ACTH and Cortisol release in the morning and in the afternoon in humans, both by itself and in combination with the opioid antagonist naloxone (Nal). Naloxone causes ACTH release in humans by removing an endogenous inhibitory opioid tone on central noradrenergic pathways stimulatory to hypothalamic corticotropin‐releasing hormone (CRH) secretion. Serotonergic agents may act directly or indirectly through these central noradrenergic pathways and, if so, would be expected to be additive to or synergistic with Nal in causing ACTH and Cortisol release.

2. Oral FX (40 mg) was given at approximately 07.00 or 11.00 h, either alone or with intravenous Nal 3 h later, to normal human volunteers. Plasma ACTH and Cortisol levels were measured for 5 h after FX dosing.

3. Fluoxetine produced a small but non‐significant increase in Nal‐stiimilated ACTH and Cortisol release in both morning and afternoon studies. Naloxone alone did not cause different ACTH and Cortisol responses in the morning and afternoon.

4. These results suggest that serotonergic pathways are not major regulators of the hypothalamic‐pituitary‐adrenal axis in humans or that FX has counteracting acute inhibitory effects on the axis, such as inhibition of hypothalamic arginine vasopressin secretion, which has been demonstrated in chronic animal studies.
EFFECTS OF 17P‐OESTRADIOL ON VASCULAR RESPONSES IN THE IN SITU BLOOD‐PERFUSED MESENTERY OF WISTAR‐KYOTO RATS
Authors: Chu ZM , Beilin LJ
Published: June 2007

1. To determine whether endogenous oestrogen plays a role in pregnancy induced decreased vascular reactivity we have examined the effects of 173‐oestradiol on vasoconstrictor responses to various stimuli using an in situ blood‐perfused mesenteric vascular preparation in Wistar‐Kyoto (WKY) rats.

2. Daily administration of 17β‐oestradiol (500 μg/kg, s.c.) for 15 days significantly enhanced mesenteric vasoconstrictor responses to noradrenaline (NA), without affecting responses to the electrical stimulation of sympathetic nerves (ES) and angiotensin II (AngII).

3. Nitric oxide (NO) synthesis inhibition by nitro‐L‐arginine methyl ester (L‐NAME; 100 mg/kg, i.v.) significantly potentiated mesenteric vasoconstrictor responses to all stimuli in both 173‐oestradiol‐treated and control animals. The difference in NA responses between groups was diminished following NO synthesis inhibition.

4. These findings do not support the hypothesis that increased endogenous oestrogen plays a role in decreased mesenteric vascular reactivity in pregnancy. However, responses to oestrogen may be dose‐dependent and enhancement of vasoconstrictor responses to NA may be relevant to oral contraceptive‐induced hypertension.
ALTERATIONS OF CARDIAC α‐ADRENOCEPTOR SUBTYPES IN HYPOTHYROID RATS
Authors: Zhang Youyi , Xu Kaiming , Han Chide
Published: June 2007

1. Alterations in the cardiac ai‐adrenoceptor and its subtypes in hypothyroid rats were studied by radioligand binding assays and reverse transcription‐polymerase chain reaction (RT‐PCR). Hypothyroidism was created by feeding rats with 0.2% 2‐thiouraciI solution instead of daily drinking water for 20 days.

2. The density of cardiac α1‐adrenoceptors (Bmax) was increased from 67.5 ± 4.3 fmol/mg in control rats to 81.1 ± 7.2 fmol/mg (P < 0.05) in hypothyroid rats.

3. Compared with control rats, in hypothyroid rats the percentages of high‐affinity sites for (+)‐niguldipine and 5‐methyl‐urapidil were increased from 13.8 ± 5.6 and 31.9 ± 6.3%, respectively, to 24.9 ± 73 and 45.5 ± 2.4%, respectively (both P < 0.05), while those for BMY7378 were decreased from 37.2 ± 8.9 to 23.8 ± 8.4% (P < 0.05), respectively. The percentage of high‐affinity sites for WB4101 was not significantly different in control and hypothyroid rats (43.3 ± 9.1 and 39.4 ± 3.6%, respectively).

4. Reverse transcription‐PCR experiments revealed that the steady state levels of mRNA for otiA‐ and am‐adrenoceptors were increased, while those for ctiD‐adrenoceptor were decreased in the hearts of hypothyroid rats.

5. The concentration‐contraction response curves for noradrenaline in the presence of a β‐adrenoceptor antagonist in control and hypothyroid rats showed that the maximal response was reduced from 344 ± 58 to 200 ± 23 mg, respectively (P < 0.05).

6. The data suggest that in hypothyroid rats the total number of cardiac ai‐adrenoceptors is increased. The change is subtype‐selective, with levels of ctiA‐ and am‐adrenoceptors being increased and levels of aiD‐adrenoceptors being reduced. Furthermore, the positive inotropic response mediated by a i‐adrenoceptors is reduced in hypothyroid rats.
A LOW DOSE OF STREPTOZOTOCIN PREVENTS KAINIC ACID‐INDUCED SEIZURES AND LETHAL EFFECTS IN THE RAT
Authors: Kim Hyoung‐Chun , Im Doo‐Hyun , Jhoo Wang‐Kee , Kim Chin , Wie Myung‐Bok
Published: June 2007

1. The effect of streptozotocin (STZ), a nitric oxide (NO) donor, on kainic acid (KA)‐induced neurotoxicity was examined in Sprague‐Dawley rats.

2. The administration of KA (8mg/kg, i.p.) produced significant neurotoxicity accompanied with increased immuno‐reactivity for Fos‐related antigen in the rat hippocampus.

3. Pretreatment with STZ (15mg/kg, i.m.) significantly blocked the neurotoxicity induced by KA.

4. Thus, the neuroprotective effect of STZ may, at least in part, reflect the role of NO in inhibiting seizures.