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Michel FS, Man RYK, Vanhoutte PM. Increased spontaneous tone in renal arteries of spontaneously hypertensive rats. Am J Physiol Heart Circ Physiol 2007; 293:H1673-81. [PMID: 17557920 DOI: 10.1152/ajpheart.00289.2007] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The spontaneous tone of vascular smooth muscle is augmented in hypertension. The present study examined the role of nitric oxide (NO), cyclooxygenase (COX), thromboxane A2/prostanoid (TP) and PGE2/prostanoid (EP-1) receptors, reactive oxygen species, and large-conductance Ca2+-activated K+ (BKCa) channels in the regulation of spontaneous tone in renal arteries of young and mature Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Rings of arteries, with and without endothelium, were suspended in a myograph for isometric force recording. Spontaneous tone (increase above initial tension) was observed only in arteries of mature SHR and was greater in arteries without endothelium. Nω-nitro-l-arginine methyl ester (l-NAME, an inhibitor of NO synthases) induced larger contractions in arteries of SHR than WKY. Indomethacin (a COX inhibitor), SC-19220 (an EP-1 receptor antagonist), and terutroban (a TP receptor antagonist) reduced the l-NAME-evoked contractions. Tiron (a superoxide anion scavenger), catalase (an enzyme that degrades H2O2), and deferoxamine (a hydroxyl radical scavenger) augmented the l-NAME-induced contractions in arteries of mature SHR. Charybdotoxin (a BKCa channel blocker) caused contractions in arteries of mature SHR without endothelium and in arteries with endothelium incubated with l-NAME. A decreased protein level of endothelial NO synthase, an increased release of prostacyclin, and an increased expression of EP-1 receptors were observed in arteries of mature SHR. The present study suggests that spontaneous tone is precipitated by age and hypertension. The reduced production of NO, leading to decreased activation of BKCa channels, may leave the actions of endogenous vasoconstrictors unopposed. COX products that activate EP-1 and TP receptors are involved in the development of spontaneous tone.
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Affiliation(s)
- Frédéric S Michel
- Department of Pharmacology, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong
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2
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Tokudome T, Mizushige K, Noma T, Manabe K, Murakami K, Tsuji T, Nozaki S, Tomohiro A, Matsuo H. Prevention of doxorubicin (adriamycin)-induced cardiomyopathy by simultaneous administration of angiotensin-converting enzyme inhibitor assessed by acoustic densitometry. J Cardiovasc Pharmacol 2000; 36:361-8. [PMID: 10975594 DOI: 10.1097/00005344-200009000-00012] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The purpose of our study has to determine the myocardial protective effects of the angiotensin-converting enzyme (ACE) inhibitor temocapril (TEM, 7 mg/kg/day) simultaneously administered with doxorubicin (Adriamycin). Twenty male Sprague-Dawley rats were intraperitoneally administered a cumulative dose of 15 mg/kg of doxorubicin (each dose of 1.0 mg/kg x 15) for 3 weeks, and divided into TEM-untreated and -treated rats. Seven control rats were injected with saline intraperitoneally. Body weight, hemodynamics, and echocardiographic measurements including quantitative analysis of ultrasonic integrated backscatter (IB) were obtained for 12 weeks after treatment. Finally, rats were killed for histopathologic study. At 6 weeks, end-diastolic left ventricular diameter (LVD) and percentage fractional shortening (%FS) were similar in TEM-treated and TEM-untreated rats, but cyclic variation of IB (dB) significantly decreased in TEM-untreated rats (7.3 +/- 1.2; control rats, 9.7 +/- 0.9; p < 0.01). At 12 weeks, %FS decreased in TEM-untreated rats (26.1 +/- 6.1%: TEM-treated rats, 34.2 +/- 6.2; p < 0.05), and calibrated IB (dB) in TEM-untreated rats (15.5 +/- 0.5) increased as compared with that in TEM-treated rats (12.1 +/- 0.7; p < 0.01). Interstitial collagen accumulation increased in TEM-untreated rats and was inhibited in treated rats. Simultaneous administration of TEM with doxorubicin was beneficial in preventing doxorubicin-induced myocardial damage, and myocardial tissue characterization was useful for the early detection of myocardial damage and the assessment of therapy.
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Affiliation(s)
- T Tokudome
- Second Department of Internal Medicine, Kagawa Medical University, Kita, Japan
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3
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Takata M, Ueno H, Hirai T, Oh-hashi S, Yasumoto K, Inoue H. Time course of the effects of temocapril on cardiovascular structure and function in patients with essential hypertension. J Cardiovasc Pharmacol 1999; 34:561-6. [PMID: 10511132 DOI: 10.1097/00005344-199910000-00013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
To investigate the time course of cardiovascular structural changes in patients with essential hypertension after angiotensin-converting enzyme (ACE) inhibition, we determined left ventricular structure, minimal vascular resistance in the forearm as an index of resistance vessel structure and stiffness beta of carotid artery in 15 essential hypertensive subjects during a placebo period and after 2, 6, and 12 months of temocapril treatment. Blood pressure decreased within 2 weeks, and the antihypertensive effects were noted throughout the 12-month administration period. Left ventricular mass index decreased significantly after 2 months (120+/-12 to 106+/-9 g/m2; p < 0.01) and was normalized after 12 months (88+/-6 g/m2). Postischemic minimal vascular resistance in the forearm decreased gradually from 2.1+/-0.5 to 1.6+/-0.4 PRU at month 12 of temocapril treatment. In contrast, increased stiffness index beta of carotid artery was not altered during a 1-year treatment period (11.4+/-4.9 to 11.6+/-3.8 at month 12 of treatment). These data indicated that the regression of structural changes of left ventricle and arterioles occurred gradually and progressively for 1-year treatment with ACE inhibition, but large arteries were not affected.
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Affiliation(s)
- M Takata
- The Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan
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4
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Hui C, Goto A, Yamada K, Yagi N, Nagoshi H, Sasabe M, Omata M, Sugimoto T. Relations of vascular calcium channels with blood pressure and endothelium in hypertension and with aging. JAPANESE HEART JOURNAL 1999; 40:209-25. [PMID: 10420882 DOI: 10.1536/jhj.40.209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To investigate the relationships between the activity in potential operated Ca2+ channels (POC), blood pressure, and endothelium in hypertension, we tested the contractile responses to a Ca2+ channel agonist Bay K 8644 (BAY K) in aorta from deoxycorticosterone-acetate-saline (DOCA-S) and reduced renal mass-saline (RRM-S) hypertensive rats. The effects of mechanical rubbing, N omega-Nitro-L-Arginine Methyl Ester (l-NAME) and indomethacin were also examined. Sensitivity to BAY K increased in experimental rats before they became hypertensive and contractile responses were enhanced as hypertension developed. Force development to BAY K was correlated with blood pressure levels. Endothelium removal enhanced the contractile response to BAY K. L-NAME, but not indomethacin, potentiated the response to BAY K. Contractile response to BAY K was negatively correlated with relaxation to acetylcholine. An enhanced contractile response to BAY K was observed also in aged rats. Enhanced activation of vascular POC in hypertension results from elevated blood pressure and partly from diminished inhibitory action of endothelium. Senescence also enhances vascular POC activity.
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Affiliation(s)
- C Hui
- Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan
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5
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Takaba H, Nagao T, Ibayashi S, Kitazono T, Fujii K, Fujishima M. Altered cerebrovascular response to a potassium channel opener in hypertensive rats. Hypertension 1996; 28:143-6. [PMID: 8675255 DOI: 10.1161/01.hyp.28.1.143] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We examined whether the effect of Y-26763, an ATP-sensitive potassium channel opener, on cerebral blood flow is altered in stroke-prone spontaneously hypertensive rats (SHRSP) and, if altered, whether long-term antihypertensive treatment with cilazapril, an angiotensin-converting enzyme inhibitor, is capable of preventing the change. Cerebral blood flow during intracarotid infusion of Y-26763 was measured in anesthetized SHRSP and normotensive Wistar-Kyoto rats (WKY) as control. Y-26763 increased cerebral blood flow in a dose-dependent manner in WKY, and glibenclamide, a selective inhibitor of ATP-sensitive potassium channels, inhibited the Y-26763-induced increase in cerebral blood flow. In contrast, the response to Y-26763 in SHRSP was significantly impaired compared with that in WKY. Antihypertensive treatment with cilazapril lowered blood pressure toward normal and prevented the impaired response in cerebral blood flow to Y-26763 in SHRSP. These findings suggest that (1) ATP-sensitive potassium channels contribute to the regulation of cerebral blood flow in rats, (2) the response to an ATP-sensitive potassium channel opener is markedly diminished in hypertensive rats, and (3) the altered response to an ATP-sensitive potassium channel opener during chronic hypertension can be prevented by long-term antihypertensive treatment.
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Affiliation(s)
- H Takaba
- Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan
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6
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Kähönen M, Arvola P, Mäkynen H, Pörsti I. Antihypertensive therapy and arterial function in experimental hypertension. GENERAL PHARMACOLOGY 1996; 27:221-38. [PMID: 8919635 DOI: 10.1016/0306-3623(95)02015-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
1. Alterations in the function of the endothelium and arterial smooth muscle may be important in the establishment of hypertension. Thus, the possible favorable influences of blood pressure-lowering agents on vascular responsiveness may be important in the chronic antihypertensive actions of these compounds. 2. A number of reports have suggested that ACE inhibitors can improve arterial function in hypertension, whereas the knowledge about the vascular effects of other antihypertensive drugs, like beta-blockers, calcium channel blockers, and diuretics remains rather limited. 3. In this article, the effects of antihypertensive therapy on arterial function in human and experimental hypertension are reviewed.
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Affiliation(s)
- M Kähönen
- Medical School, University of Tampere, Finland
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7
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Mizuno M, Sada T, Ikeda M, Fukuda N, Miyamoto M, Yanagisawa H, Koike H. Pharmacology of CS-866, a novel nonpeptide angiotensin II receptor antagonist. Eur J Pharmacol 1995; 285:181-8. [PMID: 8566137 DOI: 10.1016/0014-2999(95)00401-6] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
CS-866, (5-methyl-2-oxo-1,3-dioxolen-4-yl)methoxy-4-(1-hydroxy-1- methylethyl)-2-propyl-1-(4-[2-(tetrazol-5-yl)-phenyl]phenyl)met hylimidazol- 5-carboxylate, a prodrug type angiotensin receptor antagonist, is deesterified to the active acid, RNH-6270. RNH-6270 inhibited [125I]angiotensin II binding to bovine adrenal cortical membranes (angiotensin AT1 receptors) with an IC50 value of 7.7 nM, but not [125I]angiotensin II binding to bovine cerebellar membranes (angiotensin AT2 receptors), indicating the selectivity of the compound for angiotensin AT1 receptors. In guinea pig aortas, RNH-6270 reduced the maximal response of the concentration-contractile curve for angiotensin II (pD'2 = 9.9), but had no effect on the contractile response induced by phenylephrine or KCl. In conscious rats, intravenously injected RNH-6270 inhibited angiotensin II-induced pressor responses in a dose-dependent manner, and orally administered CS-866 produced a long-lasting inhibition of angiotensin II pressor responses. SK&F-525A, a P-450 inhibitor, suppressed the angiotensin II inhibitory effect of losartan, but not that of CS-866. These results demonstrate that RNH-6270 is a potent and AT1-selective angiotensin receptor antagonist and that, after oral administration, CS-866 has a long-lasting angiotensin II inhibitory action which is not affected by drug metabolizing enzymes in the liver.
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Affiliation(s)
- M Mizuno
- Pharmacology and Molecular Biology Research Laboratories, Sankyo Co., Ltd., Tokyo, Japan
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8
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Traub O, Lloyd MC, Webb RC. Long-term effects of brief antihypertensive treatment on systolic blood pressure and vascular reactivity in young genetically hypertensive rats. Cardiovasc Drugs Ther 1995; 9:421-9. [PMID: 8527352 DOI: 10.1007/bf00879031] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Recent studies have shown that angiotensin converting enzyme (ACE) inhibitor treatment in young spontaneously hypertensive rats (SHR) reduces blood pressure into adulthood. This study explored changes in vascular reactivity in adult normotensive (WKY) rats and stroke-prone SHR (SHRSP) receiving the following treatments at 6-10 weeks of age: (a) ACE inhibitor (ramipril); (b) hydralazine/hydrochlorothiazide (hydral/HCTZ); or (c) no treatment. The hypothesis tested was that vascular changes and blood pressure would be reduced in adult SHRSP treated with ramipril during development. At 17 weeks of age, rats were anesthetized and vascular tissue was excised. Isolated experiments in the aorta included characterization of initial phasic and tonic contractions to 0.1 microM angiotensin II (AII). A phenylephrine (PE) concentration-response curve was performed on carotid arteries, and threshold values were determined. All WKY groups showed lower systolic blood pressure (131 +/- 4 mmHg) and reduced phasic AII induced contraction (7.4 +/- 4.7%) compared with SHRSP (217 +/- 4 mmHg; 37.2 +/- 4%). Antihypertensive treatment reduced blood pressure (ramipril: 168 +/- 2; hydral/HCTZ: 198 +/- 6 mmHg) but not phasic AII responses in adult SHRSP; adult WKY rats were unaffected by treatment. Threshold values for PE in carotid arteries were lower in SHRSP than in WKY, indicating increased sensitivity. However, SHRSP treated with ramipril did not demonstrate increased sensitivity to PE. These data support the hypothesis that blood pressure and sensitivity to PE but not contractile responsiveness to AII in adult SHRSP are determined by an AII-sensitive mechanism during development.
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Affiliation(s)
- O Traub
- Department of Physiology, University of Michigan, Ann Arbor 48109-0622, USA
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9
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Watts SW, Traub O, Webb RC. Effects of ramipril on contractile oscillations in arteries from genetically hypertensive rats. Clin Exp Hypertens 1994; 16:881-98. [PMID: 7532066 DOI: 10.3109/10641969409078032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We have tested the hypothesis that altered vascular reactivity, specifically the appearance of spontaneous and BayK 8644 (L-type voltage gated calcium channel agonist)-induced oscillations in the carotid artery and the sarcoplasmic reticulum Ca(2+)-ATPase inhibitor cyclopiazonic acid (CPA)-induced oscillations in the aorta from stroke-prone spontaneously hypertensive rats (SHRS), are dependent upon angiotensin II production early in life. SHRSP and normotensive Wistar-Kyoto (WKY) rats were treated from 6-10 weeks of age with vehicle, hydralazine/hydrochlorothiazide (used as a control for lowered blood pressure) or the angiotensin converting enzyme inhibitor ramipril (3 mg/kg/day). Systolic blood pressures were measured weekly in rats from 6 to 17 weeks of age. In SHRSP (at 17 weeks of age), ramipril-treatment but not hydralazine/hydrochlorothiazide attenuated the long term expression of elevated systolic blood pressure in adult SHRSP while blood pressures of all adult WKY rats were unaffected by any treatment. At 17 weeks, rats were killed and arteries removed for in vitro measurement of isometric contractile activity. Only the incidence of spontaneous oscillations (carotid artery) was affected by ramipril treatment; ramipril did not change the frequency of BayK 8644-induced oscillations in the artery or the frequency of CPA-induced oscillations in aorta from either SHRSP or WKY. These data indicate that while spontaneous oscillations in the carotid artery may be dependent on an angiotensin II-sensitive mechanism during development, agonist-induced oscillations (CPA and BayK 8644) appear not to be angiotensin II-dependent. Thus, not all of the contractile oscillations which appear in vascular smooth muscle from SHRSP are angiotensin II-dependent, suggesting that some of these vascular abnormalities may develop at a time separate from that in which increased blood pressure is firmly established and may not be associated with the for maintenance of elevated blood pressure.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Age Factors
- Angiotensin II/physiology
- Animals
- Aorta/drug effects
- Aorta/physiopathology
- Blood Pressure
- Carotid Arteries/drug effects
- Carotid Arteries/physiopathology
- Hypertension/genetics
- Hypertension/physiopathology
- In Vitro Techniques
- Indoles/pharmacology
- Male
- Muscle Contraction/drug effects
- Muscle Contraction/physiology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiopathology
- Oscillometry
- Ramipril/pharmacology
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Vasoconstriction/drug effects
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Affiliation(s)
- S W Watts
- Department of Physiology, University of Michigan, Ann Arbor 48109-0622
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10
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Ikeda S, Amano Y, Adachi-Akahane S, Nagao T. Binding of [3H](+)-PN200-110 to aortic membranes from normotensive and spontaneously hypertensive rats. Eur J Pharmacol 1994; 264:223-6. [PMID: 7851487 DOI: 10.1016/0014-2999(94)00534-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We report here the quantitative evaluation of binding density (Bmax) of [3H](+)-PN200-110 in aortic membranes obtained from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. At both 4 and 13 weeks of age, there were no significant differences in Bmax and the dissociation constants (Kd) of [3H](+)-PN200-110 binding between SHR and WKY rat aortas. Irrespective of strain, the Kd increased and the Bmax decreased with age. These results suggest that the number of Ca2+ channels in aortas of SHR and WKY rats are not significantly different, even when hypertension is established in SHR.
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Affiliation(s)
- S Ikeda
- Department of Toxicology and Pharmacology, Faculty of Pharmaceutical Sciences, University of Tokyo, Japan
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11
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Tepel M, Ruess C, Mehring N, Neusser M, Zidek W. Effect of inhibition of sarcoplasmic Ca(2+)-ATPase on vasoconstriction and cytosolic Ca2+ in aortic smooth muscle from spontaneously hypertensive and normotensive rats. Clin Exp Hypertens 1994; 16:493-506. [PMID: 7920457 DOI: 10.3109/10641969409067958] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
To evaluate the influence of the sarcoplasmic Ca(2+)-ATPase, isometric vasoconstrictions of aortic strips from spontaneously hypertensive rats from the Münster strain (SHR) and normotensive Wistar-Kyoto rats (WKY) were measured after inhibition of Ca(2+)-ATPase by thapsigargin. Inhibition of Ca(2+)-ATPase by thapsigargin caused a biphasic contractile response of the aorta in both SHR and WKY (maximum increase of tension: 1.7 +/- 0.3 x 10(-3) Newton and 2.1 +/- 0.3 x 10(-3) Newton, respectively; mean +/- SE). The second peak of the contractile response was abolished in the absence of external calcium or by inhibition of transplasmamembrane calcium influx by nifedipine, indicating that the second peak occurs as a consequence of calcium influx from the extracellular space. The initial peak of the contractile response after thapsigargin administration was abolished in the presence of an intracellular calcium antagonist, 8-(diethylamino-)-octyl-3,4,5-trimethoxybenzoate (TMB-8), indicating that the initial response was due to calcium release from intracellular stores. Measurements using the fluorescent dye fura2 showed that thapsigargin increased the cytosolic free calcium concentration ([Ca2+]i) in SHR by 72.6 +/- 7.3 nmol/l (n = 34) and in WKY by 53.3 +/- 6.6 nmol/l (n = 39), showing no significant differences between the two strains. The inhibition of Ca(2+)-ATPase increases [Ca2+]i and causes vasoconstriction. The vasoconstriction produced by thapsigargin is not significantly different between SHR and WKY.
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Affiliation(s)
- M Tepel
- Medizinische Universitäts-Poliklinik, University of Münster, Germany
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12
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Marwood JF. The interaction between enalaprilat and selected alpha-adrenoceptor antagonists in isolated rat tail arteries. Clin Exp Pharmacol Physiol 1994; 21:417-25. [PMID: 7955551 DOI: 10.1111/j.1440-1681.1994.tb02536.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
1. Isolated perfused rat tail artery preparations were used to investigate the effects of the angiotensin converting enzyme inhibitor enalaprilat on the actions of a series of alpha-adrenoceptor antagonists. The agonist used was phenylephrine. 2. Enalaprilat (1 mumol/L) potentiated the competitive alpha 1-adrenoceptor antagonist actions of phentolamine (10-100 nmol/L) and yohimbine (0.3-3.0 mumol/L) as well as the non-competitive antagonist action of phenoxybenzamine (50-100 pmol/L). 3. The competitive alpha 1-adrenoceptor antagonist action of prazosin (1-10 nmol/L) was not affected by enalaprilat. 4. For the competitive alpha 1-adrenoceptor antagonists, including prazosin, there appeared to be an inverse relationship between antagonist potency and the extent of potentiation by enalaprilat. 5. The results support the hypothesis and angiotensin II modulates vascular smooth muscle alpha 1-adrenoceptor function.
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Affiliation(s)
- J F Marwood
- Clinical Pharmacology Department, Royal North Shore Hospital, St Leonards, New South Wales, Australia
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13
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Tokoo M, Oguchi H, Sato K, Terashima M, Miyasaka M, Kasahara H, Saito H, Kawahara Y, Shioys H, Furuta S. Single Dose Pharmacokinetics of Temocapril, an ACE Inhibitor with Preferential Biliary Excretion, in Dialysis Patients. Clin Drug Investig 1994. [DOI: 10.1007/bf03257417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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14
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Yang ST, Faraci FM, Heistad DD. Effects of cilazapril on cerebral vasodilatation in hypertensive rats. Hypertension 1993; 22:150-5. [PMID: 8340150 DOI: 10.1161/01.hyp.22.2.150] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Endothelium-dependent dilatation of cerebral arterioles is impaired during chronic hypertension. The goal of this study was to determine the effects of an angiotensin converting enzyme inhibitor, cilazapril, on endothelium-dependent dilatation in pial arterioles. Four-month-old Wistar-Kyoto (WKY) rats and stroke-prone spontaneously hypertensive rats (SHRSP) received cilazapril in their drinking water (500 mg/L) for 3 to 6 months. Treatment with cilazapril reduced mean arterial pressure in both WKY rats and SHRSP and had no significant effect on baseline diameter of pial arterioles measured with a cranial window. Responses to bradykinin and A23187, but not to nitroglycerin and adenosine, were impaired in SHRSP. Cilazapril did not affect responses to bradykinin (3 x 10(-7) M) and A23187 (10(-5) M) in WKY rats but significantly increased cerebral vasodilatation in response to bradykinin (52 +/- 4% vs 27 +/- 5%) and A23187 (19 +/- 3% vs 8 +/- 3%) in SHRSP. Cilazapril also tended to increase dilator responses to nitroglycerin and adenosine in SHRSP. In another group of SHRSP, treatment with cilazapril for 4 days produced a moderate reduction in blood pressure and increased cerebral vasodilatation in response to bradykinin, A23187, and adenosine. Topical application of the active form of cilazapril (cilazaprilat) for 40 minutes also increased cerebral vasodilatation in response to bradykinin, A23187, and nitroglycerin in SHRSP. The data indicate that an angiotensin converting enzyme inhibitor enhances cerebral vasodilatation in response to endothelium-dependent agonists in SHRSP and may also increase responses to endothelium-independent agonists.
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Affiliation(s)
- S T Yang
- Department of Pharmacology, University of Iowa College of Medicine, Iowa City 52242
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15
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Storm DS, Stuenkel EL, Webb RC. Calcium channel activation in arterioles from genetically hypertensive rats. Hypertension 1992; 20:380-8. [PMID: 1381337 DOI: 10.1161/01.hyp.20.3.380] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Enhanced contractile responsiveness to the calcium channel agonist Bay K 8644 has been documented in large conduit arteries and small muscular arteries from hypertensive rats. The present study examined the effects of Bay K 8644 on the intracellular calcium concentration ([Ca2+]i) in microvessels from stroke-prone spontaneously hypertensive rats and normotensive Wistar-Kyoto rats. Using microspectrofluorometry of fura-2, [Ca2+]i was measured in smooth muscle cells localized on arteriolar fragments (15-35 microns external diameter) isolated after collagenase digestion of the pancreas. Resting [Ca2+]i in hypertensive arterioles (94 +/- 6 nM, n = 29) did not differ from that in normotensive vessels (81 +/- 4 nM, n = 40). KCl (50 mM), applied alone and in the presence of Bay K 8644 (30 nM), stimulated increases in [Ca2+]i that were reversed in calcium-free solution and with nifedipine (10 microM), consistent with activation of potential-operated calcium channels. Potassium-induced calcium transients were consistently potentiated by Bay K 8644. The change in [Ca2+]i evoked by KCl alone or in combination with Bay K 8644 did not differ between arterioles from hypertensive and normotensive rats. In 24% of the vessels from hypertensive rats and in 29% of those from normotensive rats, Bay K 8644 evoked an increase in [Ca2+]i that did not differ significantly between the two strains. The findings indicate that, in contrast to observations made in larger arteries, there is no evidence of a functional abnormality in potential-operated calcium channels in very small arterioles from genetically hypertensive rats.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Animals
- Arterioles/metabolism
- Calcium/metabolism
- Calcium Channels/physiology
- Female
- In Vitro Techniques
- Male
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- Norepinephrine/pharmacology
- Osmolar Concentration
- Phentolamine/pharmacology
- Potassium Chloride/pharmacology
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Sodium/metabolism
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Affiliation(s)
- D S Storm
- Department of Physiology, University of Michigan Medical School, Ann Arbor
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16
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Ashida T, Yoshimi H, Kawano Y, Yoshida K, Kuramochi M, Omae T. Differential modulation of norepinephrine-induced contractile response by ryanodine and verapamil in the isolated aortic ring of spontaneously hypertensive and Wistar-Kyoto rats. CLINICAL AND EXPERIMENTAL HYPERTENSION. PART A, THEORY AND PRACTICE 1991; 13:525-40. [PMID: 1934537 DOI: 10.3109/10641969109045067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Using ryanodine and verapamil, we compared the relative contributions of SR Ca2+ release and gated Ca2+ entry in arterial contractions induced by norepinephrine (NE) between spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Aortic rings of 10 SHR and 10 WKY aged 10-12 weeks were superfused in small water-jacketed tissue chambers with physiological salt solution and isometric tension was measured. The inhibition of the NE (3 x 10(-8) M)-induced contraction of aortic rings by ryanodine (10 microM) was significantly greater in WKY (40.1 +/- 6.9%) than in SHR (2.2 +/- 9.0%) (p less than 0.01). The inhibition of the NE-induced contraction by verapamil (10 microM) in the presence or absence of ryanodine (10 microM) was significantly greater in SHR than in WKY. The residual ryanodine and verapamil-insensitive component of NE-induced contraction was significantly greater in WKY than in SHR. Caffeine (5 mM)-induced contraction in the presence of verapamil and phentolamine was significantly smaller in SHR than in WKY. These results suggest that gated Ca2+ entry plays a more important role in Ca2+ control and that ryanodine-sensitive Ca2+ store is smaller, or the ryanodine receptor is altered in these tissues of SHR compared with those of WKY.
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Affiliation(s)
- T Ashida
- Department of Medicine, National Cardiovascular Center, Osaka, Japan
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Sada T, Koike H, Ikeda M, Sato K, Ozaki H, Karaki H. Cytosolic free calcium of aorta in hypertensive rats. Chronic inhibition of angiotensin converting enzyme. Hypertension 1990; 16:245-51. [PMID: 2394484 DOI: 10.1161/01.hyp.16.3.245] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Cytosolic free calcium concentration ([Ca2+]i) and muscle tension were simultaneously measured in aortic tissue isolated from spontaneously hypertensive rats (SHR), normotensive Wistar-Kyoto (WKY) rats, and SHR chronically treated with a novel angiotensin converting enzyme inhibitor, CS-622. In the presence of 2.5 mM Ca2+ in the bathing solution, aortic [Ca2+]i measured with fura-2 was higher in SHR than in WKY rats, and it was almost the same in CS-622-treated SHR and untreated WKY rats. Increase of external Ca2+ concentration from zero to 2.5 mM elicited a contraction in SHR aortas but not in aortas from both CS-622-treated SHR and untreated WKY rats. When the aortas were contracted by 60 mM K+, however, [Ca2+]i as well as developed tension was similar in the three groups. CGP-28392 (10(-6) M), a Ca2+ channel activator, induced a rhythmic activity superimposed on a gradual increase of [Ca2+]i and tension in SHR aortas but not in the aortas of CS-622-treated SHR or untreated WKY rats. Nicardipine (10(-7) M) decreased the resting [Ca2+]i and the resting tone in SHR aortas, but not in WKY rat aortas. These results suggest that SHR aortas have a higher myogenic tone due to increased [Ca2+]i than WKY rat aortas and that the increased [Ca2+]i is attributed to alterations of dihydropyridine-sensitive Ca2+ channels in SHR aortas. Further, the decrease of the vascular tone induced by long-term administration of the angiotensin converting enzyme inhibitor may be due to a reduction of increased [Ca2+]i in SHR.
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Affiliation(s)
- T Sada
- Cardiovascular Division, Sankyo Co., Ltd., Tokyo, Japan
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