bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Analysis of Renin Gene Expression in Rat Adrenal Gland
Authors: Iwai Naoharu , Shimoike Hitoshi , Kinoshita Masahiko
Published: June 2012

Abstract
We examined the mechanism of the increased renin mRNA concentration in the adrenal glands of spontaneously hypertensive rats (SHR). In 52 female F
2
rats (25 to 27 weeks of age) derived from SHR and Wistar-Kyoto rats, we determined blood pressure, renin mRNA concentration in the adrenal gland, plasma renin activity, plasma aldosterone concentration, and genotype of the renin gene. Eighteen of the F
2
rats were fed a high salt (8%) diet for 14 days. The renin mRNA concentration in the adrenal glands showed a significant correlation with the genotype of the renin gene in the normal salt diet group (
P
<.0001), whereas this relationship was not observed in the high salt diet group. Multivariate analysis revealed that the plasma aldosterone concentration in the normal diet group was significantly explained (
P
=.0004,
R
2
=.454) by plasma renin activity (
P
=.0005), the renin mRNA concentration in the adrenal gland (
P
=.0496), and the genotype of the renin gene (
P
=.0236). The SHR allele of the renin gene was associated with a lower aldosterone concentration. On the other hand, in the high salt diet group, only the genotype of the renin gene showed a significant relationship with plasma aldosterone concentration (
P
=.0237). Again, the SHR allele of the renin gene was associated with a lower aldosterone concentration. We can conclude that the higher renin mRNA concentration in the SHR adrenal glands is governed by the SHR allele of the renin gene or renin gene locus. The renin mRNA concentration in the adrenal gland exerts a minor influence on aldosterone synthesis. Paradoxically, the SHR allele of the renin gene or renin gene locus confers a lower rate of aldosterone synthesis at 25 to 27 weeks of age, the mechanism of which remains to be determined.
The Fibrinolytic System Is Not Impaired in Older Men With Hypertension
Authors: DeSouza Christopher A. , Dengel Donald R. , Rogers Marc A. , Cox Kim , Macko Richard F.
Published: June 2012

Abstract
The fibrinolytic system is thought to be impaired in older hypertensive adults, thus contributing to the elevated risk of atherothrombosis, stroke, and acute myocardial infarction in this population. However, studies that have examined the fibrinolytic system in hypertensive individuals have failed to control for the confounding effects of other metabolic risk factors, making it difficult for one to determine the independent effect of hypertension on the fibrinolytic system. The purpose of the present study was to test the hypothesis that the fibrinolytic system is not impaired in older sedentary hypertensive men when the confounding effects of cardiovascular disease, diabetes, and dyslipidemia are controlled. Plasma concentrations of tissue-type plasminogen activator antigen and activity as well as plasminogen activator inhibitor–1 antigen and activity were measured under resting conditions in 12 hypertensive (69.4±1.4 years) and 11 normotensive (65.2±1.3 years) older men. The hypertensive and normotensive subjects had similar anthropometric and metabolic characteristics. There were no significant differences between the hypertensive and normotensive men in tissue-type plasminogen antigen (7.3±0.5 versus 6.1±0.6 ng/mL) and activity (1.8±0.3 versus 1.7±0.2 IU/mL) or plasminogen activator inhibitor–1 antigen (14.1±2.3 versus 10.8±2.2 ng/mL) and activity (17.4±1.2 versus 17.5±1.8 arbitrary units [AU]/mL) levels. In addition, the molar concentration ratio of active tissue-type plasminogen activator to active plasminogen activator inhibitor–1 did not differ between the hypertensive (1:9.7±2.3 mmol/L) and normotensive (1:10.5±2.2 mmol/L) subjects, indicative of no impairment in fibrinolytic potential in either group. These results support the hypothesis that hypertension does not directly result in impaired fibrinolytic function in older adults. Furthermore, our findings suggest that abnormalities in fibrinolytic function in older hypertensive men are likely due to the primary effects of other metabolic disorders that usually accompany hypertension, such as hyperinsulinemia and dyslipidemia.
Anticipatory Blood Pressure Response to Exercise Predicts Future High Blood Pressure in Middle-aged Men
Authors: Everson Susan A. , Kaplan George A. , Goldberg Debbie E. , Salonen Jukka T.
Published: June 2012

Abstract
Increases in blood pressure during the period of emotional arousal attendant to impending exertion are well documented, yet the etiologic significance of these elevations is unknown. Research suggests that exaggerated cardiovascular responses to psychological stress may be importantly related to hypertension. We examined blood pressure reactivity in anticipation of an exercise stress test in relation to future hypertension in the Kuopio Ischemic Heart Disease Risk Factor Study, a population-based study of middle-aged men from Eastern Finland. Subjects were 508 unmedicated men with resting blood pressure less than 165/95 mm Hg who completed a bicycle ergometer stress test at baseline and whose hypertensive status was assessed at 4 years of follow-up. Systolic and diastolic reactivity were calculated as the difference between blood pressure measured after seated rest on the bicycle ergometer before initiation of exercise and mean seated resting blood pressure measured 1 week earlier. Logistic regression models adjusted for age and resting blood pressure revealed a graded association between quartiles of reactivity and risk of subsequent hypertension (≥165/95 mm Hg), with men showing systolic responses greater than or equal to 30 mm Hg or diastolic responses greater than 15 mm Hg at nearly four times the risk of becoming hypertensive (odds ratios, 3.80 [95% confidence interval, 1.90 to 7.63] and 3.65 [95% confidence interval, 1.86 to 7.17], respectively) relative to the least-reactive groups (systolic response, <10 mm Hg; diastolic response, <5 mm Hg). Adjustments for traditional risk factors for hypertension did not alter these associations. Results demonstrate the clinical significance of the pressor response in anticipation of exercise and support the hypothesis that cardiovascular reactivity to psychological challenge plays a role in the etiology of hypertension.
Pulse Pressure Correlates in Humans With a Proscillaridin A Immunoreactive Compound
Authors: Sich Beate , Kirch Ulrike , Tepel Martin , Zidek Walter , Schoner Wilhelm
Published: June 2012

Abstract
Endogenous digitalis-like factors in humans are presumably cardenolides and bufadienolides. To test whether bufadienolide-like substances may circulate in human blood, we used antibodies from rabbits against the bufadienolide proscillaridin A to measure the concentration of cross-reacting material in human plasma with an indirect enzyme-linked immunosorbent assay. IgG had an apparent affinity of 2×10
−9
mol/L for proscillaridin A. It was specific for bufadienolides and did not cross-react with cardenolides or several steroid hormones. Extraction of human plasma with ethanol and fractionation of this extract over a high-performance liquid chromatographic reverse-phase C18 column with a propanol/isopropanol gradient resulted in the separation of three peaks of increasing hydrophobicity (ED
1
, ED
2
, ED
3
) that inhibited the sodium pump of human red blood cells and cross-reacted with proscillaridin A antibodies. The concentration of the proscillaridin A immunoreactivity ED
1
in normotensive subjects had a geometric mean of 0.1 nmol/L, with a dispersion factor of 8.77. ED
1
correlated positively in a group of 60 normotensive subjects, 22 patients with hypertension, and 19 patients with chronic renal failure with mean arterial blood pressure (log ED
1
[nmol/L]=0.013×mm Hg−2.17,
r
=.25,
P
<.05), systolic pressure (log ED
1
[nmol/L]=0.010×mm Hg−2.23,
r
=.32,
P
<.01), and pulse pressure (log ED
1
[nmol/L]=0.019×mm Hg−1.80,
r
=.38,
P
<.0001). There was no correlation with other parameters of the donors. We conclude that several substances cross-reacting with proscillaridin A antibodies and inhibiting the sodium pump of human red blood cells circulate in human blood. The level of one of these substances (ED
1
) correlates with mean arterial and pulse pressures.
Effects of Cyclosporin A on the Synthesis, Excretion, and Metabolism of Endothelin in the Rat
Authors: Abassi Zaid A. , Pieruzzi Federico , Nakhoul Farid , Keiser Harry R.
Published: June 2012

Abstract
Increasing evidence suggests that endothelin, a potent vasoconstrictor, is implicated in cyclosporin A (CsA)–induced nephrotoxicity. Increased levels of urinary and circulating endothelin have been described in CsA-treated humans and animals. The exact mechanisms by which CsA induces these increases are still unknown, and no data indicate whether these elevated levels reflect increased synthesis or decreased clearance of endothelin. In the present study, we investigated the effects of CsA administration (50 mg/kg per day IP for 6 days) to rats on plasma and urinary levels of endothelin; expression of endothelin-1 (ET-1), ET-3, and endothelin-converting enzyme in renal tissue; clearance of infused
125
I–ET-1; and degradation of
125
I–ET-1 by recombinant neutral endopeptidase. Rats given CsA for 6 days developed severe renal insufficiency, as shown by a 74% decrease in creatinine clearance rate (Ccr) (
P
<.006). Ccr was remarkably improved in CsA-treated rats that received bosentan, the combined antagonist of both endothelin A and endothelin B receptors. Urinary excretion of endothelin increased from an undetectable level to 31.7±6.0 pg/24 h (
P
<.001), and plasma levels of endothelin were unchanged (2.8±0.2 to 3.1±0.2 pg/mL). Reverse transcription followed by quantitative polymerase chain reaction revealed that ET-1 mRNA in the renal medulla increased by 59% (
P
<.006), whereas the expression of both ET-3 and endothelin-converting enzyme was unchanged. In other rats, neither acute nor chronic treatment with CsA affected either the clearance of
125
I–ET-1 from the blood or the renal and pulmonary uptake of the peptide. Moreover, CsA did not affect the degradation of
125
I–ET-1 by highly purified recombinant neutral endopeptidase, a well-known endothelinase. Taken together, these data suggest that the elevated urinary endothelin levels obtained after CsA treatment originate from the kidney and reflect increased renal synthesis of ET-1. Moreover, the production of endothelin appears to be regulated at the mRNA transcription level, and expressions of ET-1 and ET-3 are regulated independently.
Platelet Lipoxygenase in Spontaneously Hypertensive Rats
Authors: Stern Naftali , Kisch Eldad S. , Knoll Esther
Published: June 2012

Abstract
We have previously reported that the nonselective lipoxygenase inhibitor phenidone is a potent hypotensive agent in the spontaneously hypertensive rat (SHR). In the present study, we examined the relationship between production of platelet 12-hydroxyeicosatetraenoic acid (12-HETE) and intra-arterial blood pressure in SHR and Wistar-Kyoto rats (WKY) using both a cross-sectional analysis and an acute pharmacological intervention. Basal generation rate of 12-HETE by platelets collected from the SHR was approximately 3.7-fold higher than in the WKY (0.86±0.24 versus 0.23±0.05 nmol/mL per 10 minutes, respectively;
P
<.01). Systolic arterial pressure was positively related to platelet 12-HETE formation rate when the entire rat population was considered (
r
=.70,
P
<.001). The specific 12-lipoxygenase inhibitor cinnamyl-3,4-dihydroxycyanocinnamate induced lowering of both arterial blood pressure and platelet 12-lipoxygenase activity in SHR. At 15 mg/kg, cinnamyl-3,4-dihydroxycyanocinnamate elicited a marked hypotensive effect in SHR but not in WKY. This reduction in arterial pressure was accompanied by an approximate 70% inhibition in platelet 12-HETE production rate. The return of high blood pressure to basal levels was associated with a significant rise in the production of platelet 12-HETE toward control values (baseline, 0.97±0.33 nmol/mL per 10 minutes; nadir of blood pressure, 0.19±0.03; resumption of basal pressure, 0.42±0.14). In contrast, captopril (15 mg/kg) induced a quantitatively similar decrease in blood pressure but had no effect on platelet 12-HETE generation rate. Thus, hypertension in SHR is linked to increased production rate of platelet 12-HETE. Acute blood pressure reduction attained during lipoxygenase inhibition but not by angiotensin converting enzyme inhibition leads to a concomitant reduction in the production of platelet 12-HETE. We speculate that since rat arterial tissue produces 12-HETE, increased 12-lipoxygenase activity in SHR may contribute to the maintenance of elevated arterial pressure in this strain.
Effect of Salt Intake and Inhibitor Dose on Arterial Hypertension and Renal Injury Induced by Chronic Nitric Oxide Blockade
Authors: Yamada Sergio Seiji , Sassaki Ana Lúcia , Fujihara Clarice Kazue , Avancini Costa Malheiros Denise Maria , De Nucci Gilberto , Zatz Roberto
Published: June 2012

Abstract
Long-term nitric oxide blockade by
N
ω
-nitro-
l
-arginine methyl ester (L-NAME) leads to severe and progressive hypertension. The role of salt intake in this model is unclear. To verify whether salt dependence in this model is related to the extent of nitric oxide inhibition, we gave adult male Munich-Wistar rats a low salt, standard salt, or high salt diet and oral L-NAME treatment at either 3 or 25 mg/kg per day. At 10 to 15 days of treatment, the slope of the pressure-natriuresis line was decreased in rats receiving low-dose L-NAME compared with untreated controls. In rats treated with the higher dose, the line was shifted to the right but remained parallel to that obtained in untreated controls. Renal vascular resistance was moderately increased in rats receiving low-dose L-NAME, whereas high-dose L-NAME induced a marked vasoconstriction that was aggravated by salt overload. Low-dose L-NAME treatment induced hypertension only when associated with sodium overload. In rats receiving high-dose L-NAME, hypertension was aggravated by sodium excess but was not ameliorated by sodium restriction. Long-term (6 weeks) L-NAME treatment was associated with progressive hypertension, which was aggravated by salt overload, and with the development of albuminuria, focal glomerular collapse, glomerulosclerosis, and renal interstitial expansion. These abnormalities were worsened by salt overload and largely prevented by salt restriction. In the model of chronic nitric oxide blockade, salt dependence is a function of the inhibitor dose, and renal injury varies directly with the level of salt intake.
Renin-Angiotensin System and Cell Communication in the Failing Heart
Authors: De Mello Walmor C.
Published: June 2012

Abstract
The influence of heart failure on the process of cell communication was investigated in cell pairs isolated from the ventricle of cardiomyopathic hamsters (11 months old) and the results compared with age-matched normal hamsters. The gap junctional conductance (gj) was measured with two voltage-clamp amplifiers. The results showed two major populations of cell pairs with respect to gj values: one with very low values (0.8 to 2.5 nS) and the other with higher values (7 to 35 nS). In normal hamsters, the most frequent gj values were in the range of 40 to 100 nS. Angiotensin II (Ang II, 1 μg/mL) caused cell uncoupling in myopathic myocytes with low gj but reduced gj by 53±6.6% (±SE) in cell pairs with higher gj values (7 to 35 nS). The effect of Ang II on gj of myopathic cell pairs was suppressed by losartan (10
−7
mol/L). In cardiomyopathic cell pairs with low gj (0.8 to 2.5 nS), enalapril (1 μg/mL) caused an appreciable increase in gj (219±20.3%), whereas in cell pairs with higher gj (7 to 35 nS), the gj increment was smaller (80±10.8%) but still larger than that seen in controls (33±5.4%). Intracellular dialysis of Ang I (10
−8
mol/L) abolished cell communication in myopathic cell pairs with low gj (0.8 to 2.5 nS) and reduced gj by 66±1.7% in the other pairs (7 to 35 nS). The effect of Ang I on gj was greatly reduced by enalaprilat (10
−9
mol/L) added to the cytosol. Dialysis of Ang II (10
−8
mol/L) into the myopathic cell reduced gj by 48±4.2%, an effect abolished by losartan (10
−8
mol/L). The results indicate that the decline in gj seen in the ventricle of cardiomyopathic hamsters is in part due to activation of the cardiac renin-angiotensin system.
Platelet Ca
2+
Is Not Increased in Stroke-Prone Spontaneously Hypertensive Rats
Authors: Ono Norihisa , Oshima Tetsuya , Ishida Mari , Ishida Takafumi , Matsuura Hideo , Kambe Masayuki , Kajiyama Goro
Published: June 2012

Abstract
We have reported that cytosolic Ca
2+
concentration ([Ca
2+
]
i
) is increased in platelets from spontaneously hypertensive rats (SHR) in both basal and thrombin-stimulated conditions. To determine whether the correlation between blood pressure and cellular Ca
2+
metabolism exists in stroke-prone SHR (SHRSP), we investigated Ca
2+
handling using fura 2 and aggregation response in platelets of 12- to 13-week-old male SHRSP, SHR, and Wistar-Kyoto rats (WKY). Systolic pressure was highest in SHRSP and lowest in WKY (213±8, 172±7, and 135±5 mm Hg, respectively). Basal [Ca
2+
]
i
was significantly higher in SHR than WKY (45.9±4.5 versus 41.2±4.8 nmol/L,
P
<.05), and that in SHRSP (40.2±2.8 nmol/L) was similar to that in WKY. Thrombin (0.1 IU/mL)–stimulated [Ca
2+
]
i
rise was greater in SHR and smaller in SHRSP than in WKY in the presence of extracellular Ca
2+
(530±50 and 408±52 versus 475±50 nmol/L, respectively;
P
<.05). The recovery rate from the peak [Ca
2+
]
i
response to thrombin was greatest in SHRSP and least in WKY. Ionomycin (5 μmol/L)–stimulated [Ca
2+
]
i
rise was similar in WKY, SHR, and SHRSP (731±97, 743±88, and 683±70 nmol/L, respectively). Thrombin-induced maximum platelet aggregation response was higher in SHR and lower in SHRSP than WKY (82±4% and 61±15% versus 73±6%, respectively;
P
<.05). In contrast to SHR, basal [Ca
2+
]
i
in SHRSP was similar to that in WKY, and thrombin-stimulated [Ca
2+
]
i
was attenuated. These results suggest that platelet Ca
2+
handling differs between SHR substrains and that an increased [Ca
2+
]
i
is not obligatory in genetically hypertensive rats.
Renin Regulation in Cultured Proximal Tubular Cells
Authors: Henrich William L. , McAllister Elizabeth A. , Eskue Audrey , Miller Tyler , Moe Orson W.
Published: June 2012

Abstract
Recent studies have documented the presence of a complete renin-angiotensin system in the proximal tubule of the kidney; however, little is known about the regulation of renin in this proximal tubular system. Therefore, we performed the present studies to learn whether the behavior of the renin system in cultured proximal tubule is similar to that of the juxtaglomerular renin system. Basal renin secretion from rabbit proximal tubular cells in primary culture was low and not affected by isoproterenol (10
−5
mol/L), diltiazem (10
−5
mol/L), or a zero-calcium bath (0 nmol/L). Only the calcium ionophore A23187 (10
−4
mol/L) significantly reduced renin secretion in these cells (from 2.44±0.37 to 1.14±0.08 ng angiotensin I/mg protein per hour,
P
<.05). When the proximal tubular cells were lysed so the effects of the test agents on intracellular renin content could be assessed, isoproterenol caused a significant twofold (107%) increase (from 2.02±0.56 to 4.18±0.81 ng angiotensin I/mg protein per hour,
P
<.05), whereas diltiazem, A23187, and zero- and high-calcium baths did not produce a significant change. The effects of these agents on renin mRNA were examined in rabbit and rat proximal tubular cells in primary culture with the use of an S
1
nuclease protection assay. Densitometry analysis of renin mRNA and either GAPDH mRNA (rat) or α-actin (rabbit) showed no significant alterations in renin mRNA abundance. In summary, these results confirm the presence of renin mRNA in cultured proximal tubular cells and suggest that a low-level, constitutive secretion of renin occurs in this system that is decreased by A23187. Moreover, the results also suggest that proximal tubular renin is regulated, albeit differently from the juxtaglomerular renin system. Finally, short-term increments in proximal tubular renin occur without a change in renin mRNA.
Inhibition of Hypertension by Peripheral Administration of Antisense Oligodeoxynucleotides
Authors: Wielbo Donna , Simon Amy , Phillips M. Ian , Toffolo Shawn
Published: June 2012

We administered liposome-encapsulated antisense oligodeoxynucleotide targeted to angiotensinogen mRNA peripherally to spontaneously hypertensive rats to test whether peripheral angiotensinogen reduction would lower their hypertensive blood pressures and to determine the role of peripheral angiotensinogen in the modulation of hypertension. Using in vitro translation techniques, we tested the sequence specificity of the antisense sequence. The selected antisense sequence decreased angiotensinogen production in vitro, enabling us to distinguish between specific and nonspecific effects. To increase the efficiency of peripheral and hepatic antisense delivery, oligonucleotides were liposome encapsulated for intra-arterial administration. Confocal microscopy was used for determination of the hepatic distribution of fluorescently labeled antisense. Encapsulated antisense molecules were seen to be distributed within liver tissue 1 hour after injection; however, little or no uptake was observed with the unencapsulated oligonucleotides. We also determined the physiological effects of antisense oligodeoxynucleotide targeted to liver angiotensinogen mRNA. Administration of liposome-encapsulated antisense significantly decreased hypertensive blood pressures to normotensive levels compared with scrambled control oligonucleotides, unencapsulated antisense, and empty liposomes (
P
=.013). These data were supported by biochemical changes elicited by the antisense treatment. Rats receiving liposome-encapsulated antisense had significantly lowered peripheral angiotensinogen and angiotensin II levels compared with control groups (
P
<.05). No significant heart rate changes were observed in the antisense or control groups. These results suggest that peripheral angiotensinogen plays a role in the maintenance of hypertensive blood pressure in this model of hypertension and that peripheral administration of antisense molecules is possible with organ-targeted delivery mechanisms.
Benidipine Improves Endothelial Function in Renal Resistance Arteries of Hypertensive Rats
Authors: Dohi Yasuaki , Kojima Masayoshi , Sato Koichi
Published: June 2012

We studied the effects of long-term antihypertensive treatment on endothelial function in renal resistance arteries from spontaneously hypertensive rats (SHR). Wistar-Kyoto rats (WKY) were used as a normotensive reference. Adult SHR were treated with benidipine (a calcium antagonist) or ecarazine (a vasodilator) for 10 weeks; the drugs caused similar reductions in blood pressure. Changes in isometric tension of rings prepared from the third-order branches of the renal arteries were recorded. Endothelium-dependent relaxations induced by acetylcholine in rings contracted with norepinephrine were smaller in SHR than in WKY. The impaired relaxation was improved by benidipine treatment, but ecarazine had no significant effect. In vitro treatment with meclofenamic acid, a cyclooxygenase inhibitor, did not alter the differences in the relaxations. In the presence of meclofenamic acid,
N
ω
-nitro-
l
-arginine methyl ester slightly reduced the relaxations; the relaxation was smaller in SHR than in WKY and was not affected by benidipine treatment. In rings contracted with 40 mmol/L KCl, the relaxations induced by acetylcholine in the presence of meclofenamic acid were smaller than those in rings contracted with norepinephrine. The relaxation was smaller in SHR than in WKY but was normalized by benidipine treatment. Thus, acetylcholine relaxes rat renal resistance arteries by releasing nitric oxide and endothelium-derived hyperpolarizing factor from the endothelium, which is impaired in SHR. Long-term benidipine treatment improves the impaired relaxation in SHR by enhancing nitric oxide–mediated relaxation.
Utility of New Electrocardiographic Models for Left Ventricular Mass in Older Adults
Authors: Rautaharju Pentti M. , Manolio Teri A. , Siscovick David , Zhou Sophia H. , Gardin Julius M. , Kronmal Richard , Furberg Curt D. , Borhani Nemat O. , Newman Anne
Published: June 2012

Several multivariate statistical models have recently been introduced for estimation of left ventricular mass from standard 12-lead electrocardiographic measurements. The validity of these algorithms has not been adequately evaluated. The objective of this investigation was to compare the associations between echocardiographic and electrocardiographic left ventricular mass values with clinical and subclinical indexes of coronary heart disease. The evaluation was performed with participants of the Cardiovascular Health Study, a population-based sample of 5201 men and women aged 65 years and older. Echocardiographic M-mode measurements of left ventricular mass were performed from videotape recordings with the use of a strictly standardized protocol. Electrocardiographic algorithms of the Novacode program and new algorithms derived from the Cardiovascular Health Study population were used for left ventricular mass prediction. Echocardiographic and electrocardiographic determinations of left ventricular mass were technically successful in 3410 (65.6%) and 5013 (96.4%) participants, respectively. The Novacode model overestimated echocardiographic left ventricular mass. Compared with the Novacode model, the new Cardiovascular Health Study electrocardiographic model, which includes adjustment for body weight, eliminated left ventricular mass prediction bias and improved the correlation between echocardiographic and electrocardiographic left ventricular mass from .33 to .54 in women and from .46 to .51 in men. Echocardiographic and electrocardiographic models both demonstrated similar and about equally strong associations with overt and subclinical disease and with risk factors for left ventricular hypertrophy. These observations demonstrate the potential utility of electrocardiographic models for left ventricular mass estimation.
Angiotensin II Type 2 Receptor mRNA Expression in the Developing Cardiopulmonary System of the Rat
Authors: Shanmugam Sadoutounissa , Corvol Pierre , Gasc Jean-Marie
Published: June 2012

Recent studies have shown that angiotensin II has a trophic action on the heart. The presence of two types of angiotensin II receptors, type 1 (AT
1
) and type 2 (AT
2
), has been reported in the rat heart. This in situ hybridization study describes the tissue and cell location of AT
2
receptor mRNA in the developing rat cardiopulmonary system, from 15 days of gestation to adulthood. Expression of AT
1A
receptor mRNA was studied in parallel for direct comparison. The aortic arch and pulmonary artery expressed high levels of AT
2
receptor mRNA from 15 days of gestation up until 15 days postpartum, whereas expression of this mRNA was observed only just before and after birth in the coronary arteries. AT
2
receptor mRNA was not detected in any cardiac muscle of the fetus, neonate, or adult. The annulus of all four heart valves expressed AT
2
mRNA from 21 days of gestation until 10 days postpartum, but no labeling was seen in the valve leaflets. The subendocardial atrial tissue showed a high level of AT
2
receptor mRNA expression during the early postnatal period, but no expression was observed in the atrial myocytes from fetal stages to adulthood. The bronchi and trachea, but not the lung parenchyma, showed a high level of AT
2
receptor mRNA expression starting from 17 days of gestation until 10 days postpartum. AT
2
receptor mRNA expression in the cardiopulmonary system is therefore transient, developmentally regulated, and mostly located in vascular structures. By these three characteristics, its expression contrasts with that of AT
1A
, which is continuously expressed in the cardiac muscle to adulthood. This spatiotemporal pattern of expression of angiotensin II receptor mRNAs during development suggests a possible role for angiotensin II in organogenesis.
Effect of Pregnancy on Mechanisms of Relaxation in Human Omental Microvessels
Authors: Pascoal Istenio F. , Umans Jason G.
Published: June 2012

We assessed mechanisms of acetylcholine- and bradykinin-induced relaxations in human omental resistance vessels. Ring segments (approximately 200 μm normalized ID) were dissected from omental biopsies obtained from women at laparotomy (nonpregnant) or at cesarean delivery (pregnant) and were studied under isometric conditions in a Mulvany-Halpern myograph. All arginine vasopressin-preconstricted vessels relaxed in a strictly endothelium-dependent manner to acetylcholine and bradykinin; maximal relaxations were not decreased by either
N
G
-nitro-
l
-arginine or indomethacin. By contrast, bradykinin failed to relax vessels that had been preconstricted with potassium gluconate. In the combined presence of
N
G
-nitro-
l
-arginine and indomethacin, addition of charybdotoxin, a selective antagonist of some calcium-sensitive potassium channels, did not inhibit maximal bradykinin-induced relaxation. By contrast, addition of 10 mmol/L tetraethylammonium chloride abolished relaxation in vessels from nonpregnant women but not in vessels from gravidas. We conclude that bradykinin relaxes these human resistance arteries in an endothelium-dependent but predominantly nitric oxide- and prostanoid-independent manner; relaxation likely depends on the action of an endothelium-derived hyperpolarizing vasodilator. Furthermore, in striking contrast to mechanistic insights from animal studies, human pregnancy appears to augment a mechanism of endothelium-dependent relaxation in these vessels that is insensitive to the inhibitors noted above. Whether a similar novel vasodilator mechanism in vivo contributes to the physiological vasodilation that characterizes human gestation or whether failure of such a mechanism might lead to preeclampsia remains the subject of future study.
Effects of Insulin on Calcium Metabolism and Platelet Aggregation
Authors: Ishida Mari , Ishida Takafumi , Ono Norihisa , Matsuura Hideo , Watanabe Mitsuaki , Kajiyama Goro , Kambe Masayuki , Oshima Tetsuya
Published: June 2012

The influence of insulin on platelets in vitro has not been exhaustively investigated. To clarify whether insulin affects Ca
2+
metabolism in platelets directly or through alteration of other systems regulating intracellular Ca
2+
homeostasis, we examined the effect of insulin both alone and in combination with prostaglandin E
1
on platelet aggregation and Ca
2+
metabolism. Incubation of rat platelets with insulin reduced thrombin-induced Ca
2+
influx but did not change thrombin-evoked release of Ca
2+
from internal stores or the size of internal Ca
2+
stores. The interactive effects of insulin with prostaglandin E
1
were only additive, and insulin did not augment the effects of prostaglandin E
1
on platelet Ca
2+
metabolism. In contrast, insulin did not inhibit thrombin-induced platelet aggregation but did augment inhibition of platelet aggregation by prostaglandin E
1
. Our results suggest that insulin inhibits platelet function by both prostaglandin E
1
–dependent and -independent mechanisms.
Angiotensin II Increases Norepinephrine Turnover in the Anteroventral Third Ventricle of Spontaneously Hypertensive Rats
Authors: Tsukashima Akira , Tsuchihashi Takuya , Abe Isao , Nakamura Kaoru , Uchimura Hideyuki , Fujishima Masatoshi
Published: June 2012

We evaluated the effect of angiotensin II (Ang II) administered by intracerebroventricular injection on norepinephrine turnover in the anteroventral third ventricle in adult spontaneously hypertensive rats (SHR, n=35) and age-matched Wistar-Kyoto rats (WKY, n=38). Ang II (100 ng) or saline (vehicle control) was administered into the cerebral ventricle 30 minutes after injection of α-methyl-p-tyrosine (250 mg/kg IP). Norepinephrine turnover was assessed by evaluation of the norepinephrine concentration before and 1 hour after such administration. The pressor response to Ang II administration was significantly greater in SHR than in WKY (+43±3 versus +23±2 mm Hg,
P
<.01). Baseline norepinephrine turnover (response to saline) was reduced in the ventral median preoptic nucleus of SHR. Ang II significantly increased norepinephrine turnover in the organum vasculosum lamina terminalis and ventral median preoptic nucleus of SHR (organum vasculosum lamina terminalis: 40±5% by Ang II versus 18±6% by saline,
P
<.05; ventral median preoptic nucleus: 32±3% by Ang II versus 21±2% by saline,
P
<.05) but not of WKY (37±5% versus 29±5%,
P
=NS, and 30±2% versus 32±3%,
P
=NS, respectively). Thus, norepinephrine turnover in the anteroventral third ventricle region induced by intracerebroventricular administration of Ang II was increased in SHR. This effect may contribute to the enhanced pressor response to central Ang II seen in this model.
Regulation of Human Renin mRNA Expression and Protein Release in Transgenic Mice
Authors: Thompson Mark W. , Smith Shane B. , Sigmund Curt D.
Published: June 2012

The renin-angiotensin system plays a major role in the regulation of blood pressure and electrolyte homeostasis in mammals. In this study, we subjected transgenic mice containing a human renin genomic construct to a variety of pharmacological and physiological manipulations to test whether expression of the human renin gene and release of active human renin is appropriately regulated in this model. These manipulations were designed to test major regulators of renin release, including angiotensin II, the macula densa, renal perfusion pressure, and β-adrenergic receptors. We used human plasma renin concentration and human renal renin mRNA levels to document the response of the transgene to these stimuli. Human plasma renin concentration increased in response to both angiotensin-converting enzyme inhibition with captopril and isoproterenol and decreased after a high salt diet. A low salt or sodium-deficient diet did not stimulate renin release. Human renin mRNA levels in kidney increased after captopril but were unchanged in the other experimental groups. We also measured the levels of human renin mRNA in double transgenic mice containing the same human renin gene in addition to the human angiotensinogen gene. These mice are chronically hypertensive and have increased circulating levels of angiotensin II. Human renin mRNA levels in the kidney were paradoxically elevated compared with their single transgenic normotensive counterparts. These transgenic mice provide a model for examination of human renin regulation and may help elucidate the molecular mechanisms that regulate the gene in response to physiological cues.
Neural Nitric Oxide Synthase in the Renal Medulla and Blood Pressure Regulation
Authors: Mattson David L. , Bellehumeur Thomas G.
Published: June 2012

We studied the effect of selective inhibition of the neural isoform of nitric oxide synthase in the rat renal medulla in conscious Sprague-Dawley rats. Continuous renal medullary interstitial infusion of an antisense oligonucleotide complementary to the initiation region of the mRNA for neural nitric oxide synthase increased blood pressure 14±1 mm Hg in rats maintained on a high sodium intake. Medullary interstitial infusion of saline vehicle or a scrambled oligonucleotide probe failed to alter blood pressure in separate groups of high salt control rats. Renal medullary interstitial infusion of the antisense oligonucleotide significantly decreased the level of neural nitric oxide synthase in the renal medulla by 53±8% and decreased total renal medullary nitric oxide synthase activity by 28±8%. No alterations were detected in the levels of inducible nitric oxide synthase or β-actin in the antisense oligonucleotide–infused rats. To confirm the antisense oligonucleotide data, we administered a mechanistically different inhibitor of neural nitric oxide synthase, 7-nitroindazole, to an additional group of rats maintained on a high salt diet. Direct renal medullary interstitial infusion of this selective enzyme inhibitor significantly increased mean arterial pressure (15±6 mm Hg) and decreased total renal medullary nitric oxide synthase activity by 37±12% in rats on a high sodium diet. The present experiments demonstrate a role for the neural isoform of nitric oxide synthase in the long-term control of blood pressure in the presence of a high salt diet.
In Vitro Alteration of Aortic Vascular Reactivity in Hypertension Induced by Chronic
N
G
-Nitro-
l
-Arginine Methyl Ester
Authors: Henrion Daniel , Dowell Fiona J. , Levy Bernard I. , Michel Jean-Baptiste
Published: June 2012

Chronic administration of
N
G
-nitro-
l
-arginine methyl ester (L-NAME) induces a rise in blood pressure that is prevented by angiotensin I–converting enzyme inhibitors or angiotensin II receptor (type 1) blockade. Alterations in vascular reactivity in this model have not been extensively studied and could potentially be involved in the pathogenesis of L-NAME–induced hypertension. In the present work, we aimed to study the vascular reactivity and cGMP content of aortic ring segments isolated from Wistar rats treated for 3 weeks with L-NAME or L-NAME plus the converting enzyme inhibitor quinapril. Quinapril prevented the rise in blood pressure in L-NAME–treated rats although acetylcholine-induced dilation in aortic rings was suppressed and sodium nitroprusside–induced dilation was increased in both L-NAME– and L-NAME plus quinapril–treated rats. In isolated aortic ring segments, chronic L-NAME decreased the contractile response to K
+
(125 mmol/L), phenylephrine, angiotensin II, the G protein stimulator AlF
4
−
, and the protein kinase C activator phorbol dibutyrate. In contrast to the upregulated sodium nitroprusside–induced dilation, the contractile capacity of the aorta in response to angiotensin II, phenylephrine, AlF
4
−
, K
+
, and phorbol dibutyrate was restored by quinapril. Aortic cGMP was lowered in rats treated with L-NAME (530±120 fmol/mg protein, n=12,
P
<.05) and L-NAME plus quinapril (461±140 fmol/mg protein, n=12,
P
<.05) compared with controls (1798±522 fmol/mg protein, n=12). We hypothesize that the continuous nitric oxide blockade by L-NAME might attenuate a continuous endogenous relaxing tone and is associated with an upregulated endogenous vasoconstrictor tone in large arteries. Converting enzyme inhibition interfered more with the increased endogenous constrictor tone than with the decreased vasodilator tone in the wall of large arteries from L-NAME–treated rats.
Ouabainlike Compound in Hypertension Associated With Ectopic Corticotropin Syndrome
Authors: Goto Atsuo , Yamada Kaoru , Hazama Hisanori , Uehara Yoshio , Atarashi Keiichiro , Hirata Yasunobu , Kimura Kenjiro , Omata Masao
Published: June 2012

Molecular mechanisms related to sodium retention have been implicated in the pathogenesis of hypertension. It is unclear how sodium retention leads to a rise in blood pressure, but ouabainlike compound may act as a final common pathway in sodium-induced hypertension. In ectopic corticotropin syndrome, hypertension has been attributed to cortisol inactivation overload, giving rise to mineralocorticoid-type hypertension. We sequentially measured plasma and urinary levels of ouabainlike compound over 2 months to evaluate its role in the hypertensive mechanisms in a 64-year-old man with this syndrome caused by lung cancer. His data included hypokalemia and increased cortisol concentrations, corticotropin levels, and urinary 17-hydroxycorticosteroid excretion. Plasma renin activity was suppressed. Plasma and urinary levels of ouabainlike compound were markedly increased concomitantly with high blood pressure. The maximum plasma level was 40-fold the normal range of the subject. After chemotherapy, ouabainlike compound levels gradually decreased in parallel with the decline in blood pressure and rise in potassium concentration. A correlation was observed between plasma and urinary levels of ouabainlike compound (
P
<.05). Plasma and urinary levels of ouabainlike compound correlated with systolic (
P
<.01) and diastolic (
P
<.05) pressures, respectively. The peak of ouabainlike compound in plasma and urine coincided with that of authentic ouabain on high-performance liquid chromatography. Ouabainlike compound derived from urine inhibited [
3
H]ouabain binding to human erythrocytes. These findings suggest that ouabainlike compound with biological activity could partly account for hypertension in ectopic corticotropin syndrome.
Angiotensin II in the Evolution of Experimental Heart Failure
Authors: Luchner Andreas , Stevens Tracy L. , Borgeson Daniel D. , Redfield Margaret M. , Bailey Jane E. , Sandberg Sharon M. , Heublein Denise M. , Burnett John C.
Published: June 2012

Although angiotensin II (Ang II) has been implicated in the pathophysiology of congestive heart failure, its temporal and regional changes during the development and progression of the disease are poorly defined. Our objective was to assess circulating, renal, cardiac, and vascular Ang II in a canine model of rapid ventricular pacing–induced heart failure that evolves from early left ventricular dysfunction to overt congestive heart failure. Ang II was measured by radioimmunoassay with low cross-reactivity to other angiotensins. Control, early left ventricular dysfunction, and overt congestive heart failure dogs were studied. Early left ventricular dysfunction was characterized by impaired cardiac function, cardiac enlargement, preserved renal perfusion pressure, maintained urinary sodium excretion, and normal plasma renin activity. Overt congestive heart failure was characterized by further impaired cardiac function and cardiac enlargement, reduced renal perfusion pressure, urinary sodium retention, and increased plasma renin activity and plasma Ang II. In early left ventricular dysfunction dogs, renal cortical, renal medullary, ventricular, and aortic Ang II were unchanged, and atrial Ang II was decreased. In overt congestive heart failure dogs, Ang II was increased in the kidney and heart compared with normal dogs and in all tissues compared with early left ventricular dysfunction dogs. The greatest increase in tissue Ang II occurred in the renal medulla. We conclude that early increases in local renal, myocardial, and vascular Ang II do not occur in this model of early left ventricular dysfunction and may even be suppressed. In contrast, increased myocardial and particularly renal Ang II in association with increased circulating Ang II are hallmarks of overt experimental congestive heart failure. These studies provide new insights into the temporal and regional alterations in Ang II during the progression of experimental congestive heart failure.
Subconstrictor Doses of Neuropeptide Y Potentiate α
1
-Adrenergic Venoconstriction In Vivo
Authors: Linder Lilly , Lautenschlager Brigitte M. , Haefeli Walter E.
Published: June 2012

The 36–amino acid human neuropeptide Y is a vasoactive compound released after stimulation of the sympathetic nervous system. In addition to its direct and long-lasting vasopressor effects, it may potentiate the constrictor action of catecholamines and other vasoconstrictors at doses that do not per se exert vascular effects. Using the hand vein compliance technique, we have previously shown that neuropeptide Y also constricts superficial hand veins and that its effects may last for several hours. In this study, we investigated the local effect of neuropeptide Y on α
1
-adrenergic venoconstriction in nine healthy volunteers at dose rates that did not affect venous compliance. On separate days, cumulative dose-response curves to phenylephrine alone and with coadministration of 1 or 30 pmol neuropeptide Y per minute were constructed, and the responses were fitted to a four-parameter logistic equation. Neuropeptide Y dose dependently shifted the phenylephrine curves toward lower dose rates without affecting maximal effects. ED
50
values for phenylephrine alone and with 1 or 30 pmol/min neuropeptide Y were 4.0, 4.9 (
P
=NS versus control), and 1.2 (
P
<.005) nmol/min, respectively. Comparison with neuropeptide Y dose-response curves revealed that the interaction was synergistic. These are the first data in humans to show that small dose rates of neuropeptide Y may potentiate α-adrenergic effects in vivo. Because this interaction occurs at estimated local concentrations nearly achieved in humans, these studies suggest that neuropeptide Y might modulate the filling of this capacitance system in vivo.
Differential Regulation of Angiotensinogen Transcripts After Renin Infusion
Authors: Milsted Amy , Nishimura Masato , Brosnihan K. Bridget , Ferrario Carlos M.
Published: June 2012

To investigate angiotensinogen regulation in high-renin hypertension, we infused porcine renin intravenously at either a low (4 mU/kg per hour, n=6) or high (20 mU/kg per hour, n=9) dose into male Sprague-Dawley rats (225 to 250 g) for 5 days using osmotic minipumps. Control rats received 0.9% NaCl. In renin-infused rats, mean arterial pressure and plasma renin activity were significantly elevated. Both low- and high-renin infusions lowered plasma angiotensinogen levels. Plasma angiotensin II was elevated in rats given renin but reached statistical significance only at the higher dose. Angiotensinogen mRNA isolated from the liver, adrenal gland, kidney, and brain was measured by slot blot analysis. Both renin doses were associated with significant decreases in the levels of liver and hypothalamic angiotensinogen mRNA. In the medulla oblongata, angiotensinogen mRNA was reduced only by the higher renin dose. The lower dose increased angiotensinogen mRNA in the adrenal gland, and in kidney, angiotensinogen mRNA level was unchanged by renin infusion. Angiotensinogen mRNA visualized on Northern blots showed that the number of mRNA species in liver decreased from three in control rats to a single mRNA species after renin infusion. Tissue differences in the size of the major angiotensinogen mRNA species were also apparent. This, together with changes in the total hybridization signal of angiotensinogen mRNA in tissues, suggests that renin differentially affects the different angiotensinogen mRNA transcripts. Results of this study indicate that angiotensinogen gene expression is regulated not only by alterations in levels of circulating angiotensin II but also by other mechanisms, presently unidentified, that are activated by renin infusions.
Disproportional Arterial Hypertrophy in Hypertensive mRen-2 Transgenic Rats
Authors: Struijker-Boudier Harry A.J. , van Essen Helma , Fazzi Gregorio , De Mey Jo G.R. , Qiu Hong Ying , Lévy Bernard I.
Published: June 2012

In the present study, we investigated the role of enhanced vascular renin-angiotensin activity in vascular hypertrophy. We used transgenic (mRen-2)27 (renin TGR) rats, spontaneously hypertensive rats (SHR), and their respective normotensive control rats to study in situ pressure-diameter relationships in second-generation mesenteric arterial branches (in vivo diameter, 400 to 500 μm) over a pressure range of 0 to 200 mm Hg. We studied pressure-diameter curves under both control (Tyrode's solution) and fully relaxed (Tyrode's solution containing 100 mg/L potassium cyanide) conditions. From these curves, we determined mechanical properties at operating blood pressure. In both hypertensive strains, mesenteric arterial media cross-sectional area was increased, with a significantly (
P
<.05) stronger degree of hypertrophy in renin TGR rats. Arterial distensibility of relaxed vessels was decreased to an equal degree in both hypertensive strains. Under control conditions, distensibility was higher in SHR than in renin TGR rats but still significantly reduced compared with distensibility in normotensive rats. Wall tension was increased to an equal degree in both hypertensive strains, whereas circumferential wall stress was normal in SHR but significantly (
P
<.05) reduced in renin TGR rats. These results indicate that whereas vascular hypertrophy in SHR causes adaptive normalization of arterial wall stress, enhanced vascular renin-angiotensin activity causes vascular hypertrophy in excess of the hypertrophy associated with pressure elevation alone.