Differences in papaverine inhibition of prostaglandin-induced contraction of aortic strips from normal and spontaneously hypertensive rats (SHR)

Papaverine was studied for its ability to inhibit prostaglandin (PG) E₂, F_2α, A₁, as well as norepinephrine (NE)-and KCl-induced contractions of aortic strips from normal and spontaneously hypertensive rats (SHR). There was a 2.8, 5.1, and 6.2 fold increase in the concentration of papaverine required 50% inhibition of PGA₁, PGF_2α and PGE₂ contractions of aortic strips from SHR compared to normal tissues. There was no significant difference in the inhibiton of NE- or KCl-induced contractions of aortae from SHR compared to controls. The relative resistance of aortae from SHR to the inhibitory effect of papaverine on pG-induced contractions may be explained in terms of the higher phosphodiesterase activity in aortae from SHR and/or possible differences in PG-induced Ca²⁺ translocation compared to normal tissue.     

Vascular protein kinase C in Wistar-Kyoto and spontaneously hypertensive rats.

Phorbol esters which activate protein kinase C (PKC) produced concentration-related force development in aorta from spontaneously hypertensive rat (SHR) and Wistar-Kyoto rat (WKY); all were 2-7 x more potent in SHR. However, total PKC activity in aortas, as well as carotid, caudal and renal arteries, was not different, when SHR was compared with WKY. Binding of phorbol dibutyrate to particulate aortic PKC was similar in SHR and WKY (same apparent Kd and Bmax values), as was potency for displacement of phorbol dibutyrate by phorbol myristate acetate. Furthermore, there was no difference in potency with staurosporine, H-7, and calmidazolium in inhibiting SHR and WKY aortic PKC. These data demonstrate enhanced contractile sensitivity to PKC-activating phorbol esters in SHR aortic smooth muscle that is not related to activity, phorbol ester binding, or sensitivity to inhibitors when SHR PKC is compared with WKY PKC. Thus, signal transduction events distal to PKC activation may be responsible for enhanced vascular contractile sensitivity to phorbol esters in SHR.     

p38 Mitogen-activated protein kinase regulates vasoconstriction in spontaneously hypertensive rats

We investigated whether p42/p44 mitogen-activated protein kinase (MAPK) and/or p38 MAPK participates in the regulation of vascular smooth muscle contraction by endothelin-1 (ET-1) in Wistar-Kyoto rat (WKY) and spontaneously hypertensive rat (SHR). ET-1 (10 nM) induced a sustained contraction in WKY and SHR aortas. PD98059 (100 microM), an inhibitor of p42/p44 MAPK kinase, partially attenuated the ET-1-induced contraction in WKY and SHR. However, SB203580 (10 microM), an inhibitor of p38 MAPK, relaxed the ET-1-induced contraction to the resting levels in SHR, but not in WKY. ET-1 (10 nM) increased phosphorylation of both p42/p44 MAPK and p38 MAPK in WKY and SHR. However, in SHR, p38 MAPK phosphorylation in response to ET-1 stimulation was increased more than in WKY. PD98059 (100 microM) and SB203580 (10 microM) abolished the phosphorylation of p42/p44 MAPK and p38 MAPK in response to ET-1 stimulation in WKY and SHR, respectively. On the other hand, SB203580 (10 microM) did not affect myosin light chain (MLC) phosphorylation in response to ET-1 (10 nM) stimulation in WKY and SHR. From these results, it is concluded that p42/p44 MAPK and/or p38 MAPK partially regulates the ET-1-induced vasoconstriction in WKY. However, p38 MAPK, rather than p42/p44 MAPK, activation plays an important role for the maintenance of ET-1-induced vasoconstriction in SHR through a MLC phosphorylation-independent pathway.     

Altered mitogen-activated protein kinase activation in vascular smooth muscle cells from spontaneously hypertensive rats

1. We previously reported that activation function of mitogen-activated protein kinases (MAPK) is enhanced in aorta strips from both prehypertensive and hypertensive spontaneously hypertensive rats (SHR) and that this enhancement of MAPK activation results from enhanced MAPK activation reactivity to angiotensin (Ang) II in SHR aorta strips. 2. The purpose of the present study was to examine whether the enhanced function of the vascular angiotensin system observed in SHR aorta strips results from genetic alterations of vascular smooth muscle cells from SHR. 3. Basal MAPK activity was within normal limits in cells from 4-week-old SHR, whereas enzyme activity was enhanced in 9-week-old SHR compared with age-matched Wistar-Kyoto (WKY) rats. 4. Mitogen-activated protein kinase activation reactivity to AngII and endothelin-1 was enhanced in 9-week-old SHR cells but not in 4-week-old SHR cells. The enhancement of basal MAPK activity in 9-week-old SHR cells was abolished by a combination of the angiotensin AT(1) receptor antagonist losartan and the endothelin receptor antagonist BQ123. 5. These findings suggest that MAPK activation function in 4-week-old SHR cells is not enhanced. Thus, it appears that factors outside vascular smooth muscle cells are needed for the enhanced MAPK activation observed in 4-week-old SHR aorta strips. In 9-week-old SHR, MAPK activation function is enhanced in cells themselves and this function may, at least in part, contribute to the enhanced MAPK activation observed in SHR aorta strips.     

Effects of ovariectomy on naloxone-modulated hypertension in spontaneously hypertensive rats (SHR)

Ovariectomy was performed at 4 weeks of age (W), and the rats were used when they were 33 and 75 W old. Systolic blood pressure (BP) was measured by the tail-cuff method. Naloxone (10 mg/kg) was given i.p. Catecholamines (CA) were determined with HPLC. Norepinephrine (NE) was not significantly altered in intact rats by naloxone; however, a significant increase in NE appeared in the plasma, hippocampus, thalamus plus mid-brain and hypothalamus in castrated rats following naloxone. With naloxone treatment, dopamine (DA) was significantly increased in the plasma and hypothalamus, but decreased in the cerebral cortex in intact rats; and with castrated rats, there was a tendency to see an increase in plasma DA and significantly increased levels of DA in the thalamus plus mid-brain and hypothalamus. This suggests that in female brain, lack of estrogen in the castrated rats leads to an increase in intrinsic opiate, and this in turn inhibits CA release. On the other hand, when naloxone was administered to castrated rats, intrinsic opiate was blocked, and, consequently, inhibition of CA release was lost and induction of CA release was enhanced.     

Oscillations and cysteine metabolism in aortic strips of hypertensive rats.

Aortic strips of normal and hypertensive rats were used for the study. In comparison with normal rats hypertensive rats show a low cysteine and high homocysteine level and vascular auto-oscillations. The auto-oscillations are damped by cysteine, cAMP, theophylline and heparin but not by ADP.     

Effects of 6-hydroxydopamine on spontaneously hypertensive rats

Summary In order to evaluate the role of the sympathetic nervous system in the development and maintenance of spontaneous hypertension, spontaneously hypertensive and normotensive rats were give 6-hydroxydopamine (6-OH-dopamine).A single i.v. dose of 6-OH-dopamine (100 mg/kg) caused a biphasic rise in blood pressure in both hypertensive and normotensive rats.During long-term treatment the first dose of 6-OH-dopamine (25 or 50 mg/kg i.v.) lowered the blood pressure, measured 24 h after injection, two or three times more in hypertensive than in normotensive rats. As a result, the blood pressure reached the same level in both groups, i.e. 90–100 mm Hg. Within three days this hypotension subsided. After repeated weekly administration of 6-OH-dopamine the depressor effect declined gradually and after 4 weeks it was no longer significant. When this stage was reached, adrenal demedullation as such neither lowered the basal blood pressure, nor prevented the development of tolerance to 6-OH-dopamine. Accordingly, the adrenal medulla is not decisive in maintaining the blood pressure and in the development of tolerance to the depressor effect of 6-OH-dopamine in spontaneously hypertensive and normotensive animals.After treatment with 8 weekly doses of 6-OH-dopamine, the pressor response to noradrenaline increased in both hypertensive and normotensive rats, while the response to tyramine decreased.When, on the second day after birth, new-born rats of the hypertensive strain were given a single dose of 6-OH-dopamine (50 mg/kg i.p.) the development of hypertension was inhibited to some degree. This inhibition was more marked when the animals were given weekly doses of 6-OH-dopamine (50 mg/kg i.p.) during 5 weeks. On the other hand, when pregnant rats of the same strain received 6-OH-dopamine (50 mg/kg i.v.) twice during the last week before delivery, the offsprings did develop hypertension.It is evident that the adrenergic nervous system plays an important part in the development of hypertension in rats of a spontaneously hypertensive strain, but it is no longer of essential importance once the hypertension is established.Partly presented at the Fifth International Congress on Pharmacology, San Francisco, July 23–28, 1972 (Neuvonen et al., 1972).     

Effects of sodium loading on antihypertensive responses to an angiotensin-converting enzyme inhibitor in spontaneously hypertensive and renal hypertensive rats

Sodium loading significantly attenuated the antihypertensive potency of an angiotensin-converting enzyme inhibitor, SA446, in 2-kidney, 1-clip renal hypertensive rats, but the potency of SA446 remained unchanged in spontaneously hypertensive rats. Basal levels of plasma renin activity of both types of hypertensive rats were suppressed by sodium loading. From these results, it appeared that a different mechanism was involved in the maintenance of hypertension in 2-kidney, 1-clip renal hypertensive rats and in spontaneously hypertensive rats. It also appeared that the mechanism of the antihypertensive action of angiotensin-converting enzyme inhibitors was not explainable only by the suppression of the plasma renin-angiotensin system.     

The protein kinase C inhibitor H-7 inhibits concanavalin A induced T-lymphocyte activation

1. 1-(5-isoquinoline sulfonyl)-2-methylpiperazine (H-7), a protein kinase C inhibitor, was found to inhibit con A stimulated [3H]thymidine incorporation and cytosolic protein kinase C (PKC) activation in T-lymphocytes of mouse spleen. 2. The inhibitory effect of H-7 was both concentration and time-dependent. 3. H-7 exerted no inhibition when T-lymphocytes have been preincubated with con A for 10 hours or longer. 4. These results support the notion that PKC is an important element of the con A mitogenic signal transduction mechanism and the PKC signal is completed within the first 10 hr of con A incubation.     

Mitogen-activated protein kinase contributes to elevated basal tone in aortic smooth muscle from hypertensive rats

The role of mitogen-activated protein kinase (MAPK) in increased basal tone -spontaneous resistance in vascular muscle strips- was clarified in aortic smooth muscle from deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The MAPK/extracellular signal-regulated protein kinase (ERK) kinase inhibitor, PD098059 (2'-amino-3'-methoxyflavone), significantly inhibited basal tone in a dose-dependent manner. The basal level of ERK1/2 activation was inhibited by PD098059 and was significantly greater in hypertensive rats than in sham-operated rats. In contrast, inhibition with PD098059 was not observed in sham-operated rats. GF109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)maleimide), an inhibitor of protein kinase C (PKC), decreased both basal tone and ERK1/2 activity in the hypertensive rats. In contrast, Y27632 ((R)-(+)-trans-N-(4-Pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide) and verapamil, inhibitors of Rho kinase and voltage-dependent Ca2+ channels, respectively, significantly inhibited basal tone but not ERK1/2 activity. Thus, basal vascular tone is elevated by the altered activation of MAPK in DOCA-salt hypertensive rats, and this is regulated by PKC, but not by Rho or intracellular Ca2+.     

Angiotensin-(1-7) blockade attenuates captopril- or hydralazine-induced cardiovascular protection in spontaneously hypertensive rats treated with NG-nitro-L-arginine methyl ester

We assessed the contribution of angiotensin-(1-7) [Ang-(1-7)] to captopril-induced cardiovascular protection in spontaneously hypertensive rats (SHRs) chronically treated with the nitric oxide synthesis inhibitor NG-nitro-L-arginine methyl ester (SHR-l). NG-nitro-L-arginine methyl ester (80 mg/L) administration for 3 weeks increased mean arterial pressure (MAP) from 196 ± 6 to 229 ± 3 mm Hg (P < 0.05). Treatment of SHR-l with Ang-(1-7) antagonist [d-Ala7]-Ang-(1-7) (A779; 744 μg·kg(-1)·d(-1) ip) further elevated MAP to 253 ± 6 mm Hg (P < 0.05 vs SHR-l or SHR). Moreover, A779 treatment attenuated the reduction in MAP and proteinuria by either captopril (300 mg/L in drinking water) or hydralazine (1.5 mg·kg(-1)·d(-1) ip). In isolated perfused hearts, the recovery of left ventricular function from global ischemia was enhanced by captopril or hydralazine treatment and was exacerbated with A779. The Ang-(1-7) antagonist attenuated the beneficial effects of captopril and hydralazine on cardiac function. Recovery from global ischemia was also improved in isolated SHR-l hearts acutely perfused with captopril during both the perfusion and reperfusion periods. The acute administration of A779 reduced the beneficial actions of captopril to improve recovery after ischemia. We conclude that during periods of reduced nitric oxide availability, endogenous Ang-(1-7) plays a protective role in effectively buffering the increase in blood pressure and renal injury and the recovery from cardiac ischemia. Moreover, Ang-(1-7) contributes to the blood pressure lowering and tissue protective actions of captopril and hydralazine in a model of severe hypertension and end-organ damage.     

奈比洛尔对自发性高血压大鼠循环和主动脉肾素-血管紧张素系统的影响

目的：探讨奈比洛尔（Nebivolol）对自发性高血压大鼠循环和主动脉肾素-血管紧张素系统（RAS）的影响。方法：18只自发性高血压大鼠（SHR）和6只同源正常血压大鼠Wistar-Kyoto（WKY）随机分为：（1）奈比洛尔组（n=6）：SHR给予奈比洛尔5mg·kg-1·d-1;（2）卡托普利组（n=6）：SHR给予卡托普利15mg·kg-1·d-1;（3）SHR对照组（n=6）;（4）WKY对照组（n=6）。奈比洛尔、卡托普利溶于蒸馏水中灌胃,对照组给予等体积蒸馏水灌胃。给药8周后测定血浆肾素活性（PRA）,血浆和主动脉血管紧张素Ⅱ（AngⅡ）、一氧化氮（NO）浓度,NO/AngⅡ和血管紧张素转化酶（ACE）活性。结果：与WKY比较,SHR血浆和主动脉NO含量降低,AngⅡ水平显著增加,NO/AngⅡ降低;主动脉ACE活性明显增加,而血浆ACE活性则降低;但PRA在两组间无显著性差异。奈比洛尔治疗对SHR血浆AngⅡ含量和ACE活性无影响,但可降低主动脉AngⅡ水平,抑制主动脉ACE活性,从而增加血浆及主动脉NO含量和NO/AngⅡ。结论：奈比洛尔抑制肾素-血管紧张素系统,可能是其降低血压的机制之一。     

Effects of an angiotensin-converting enzyme (ACE) inhibitor, SA446, on tissue ACE activity in normotensive, spontaneously hypertensive, and renal hypertensive rats

Effects of an angiotensin-converting enzyme (ACE) inhibitor, SA446, on the renin-angiotensin system, particularly on tissue ACE activity, were studied in Wistar-Kyoto normotensive rats (WKY), spontaneously hypertensive rats (SHR), and two-kidney, one-clip renal hypertensive rats (RHR) by repeated oral administration for 7 days. SA446 (45 mg/kg/day p.o.) inhibited ACE activity in the lung, brain, kidney, heart, and whole blood throughout the administration period in WKY, but showed a slight hypotensive action and no inhibition of aorta ACE activity. On the other hand, SA446 had an apparent hypotensive action at the same dose in SHR and inhibited ACE activity significantly in the aorta as well as the kidney and whole blood during the administration period. Furthermore, enzyme activity in the aorta, kidney, heart, and whole blood was also inhibited at a hypotensive dose of SA446 (10 mg/kg/day p.o.) in RHR. The inhibition in whole blood and kidney was almost complete, and the inhibition in the aorta was greater on day 7 than on day 1. The maximum decrease of blood pressure was correlated with the maximum inhibition in aorta ACE activity, but not in brain, lung, or heart ACE activity. In addition, a good positive correlation was observed between the basal blood pressure and the basal aorta ACE activity in WKY, SHR, and RHR, although there was no correlation in the brain, lung, kidney, heart, or whole blood. These results suggest that the antihypertensive action of SA446 by repeated administration may be due to inhibition of arterial ACE activity in addition to inhibition of plasma and kidney ACE activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protein kinase C activity in blood vessels from normotensive and spontaneously hypertensive rats.

This study investigates the effects of phorbol dibutyrate (PDB) on protein kinase C (PKC) activation, as assessed by the translocation of PKC activity from the cytosolic to the particulate fraction, in aortas and mesenteric arteries from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). The basal distribution of PKC activity between the cytosolic and particulate fractions of SHR and WKY aortas, and mesenteric arteries, was not significantly different. PDB induced a concentration-dependent decrease in cytosolic PKC activity in SHR and WKY aortas. PDB (0.01 microM) decreased cytosolic PKC activity to a greater magnitude in SHR aorta as compared to WKY aorta, while 1.0 microM PDB decreased cytosolic PKC activities to similar magnitudes in SHR and WKY aortas, and mesenteric arteries. These results suggest that the increased sensitivity of SHR vessels to contraction by phorbol esters may be due, at least in part, to the greater sensitivity of PKC in these vessels to phorbol ester activation.     

Effects of phorbol ester on carbachol-induced contraction in bovine ciliary muscle: possible involvement of protein kinase C

The aim of the research was to characterize muscarinic receptors of bovine ciliary muscle and to investigate the desensitization process. The role of protein kinase C was analyzed. The results show that muscarinic receptors of bovine ciliary muscle have the pharmacological characteristics of the M₃ subtype. Acute exposure to phorbol esters (1 μM phorbol 12,13-dibutyrate, PDB, or 0.1 μM phorbol 12-myristate 13-acetate, PMA, for 15 and 5 min, respectively) resulted in antagonism of muscarinic receptor-mediated contraction. Long-term pretreatment (18 h) with PMA to down-regulate protein kinase C resulted in potentiation of carbachol-induced contraction, reduction of agonist-induced desensitization and loss of phorbol ester-induced desensitization. Staurosporine (3 μM) and H₇ [1-(5-isoquinolinesulfonyl)-2-methyl-piperazine] (1 μM), protein kinase C inhibitors, produced a significant potentiation of the contractile effect of carbachol, reduced the desensitization produced by repeated addition of carbachol and suppressed that induced by phorbol esters. In vitro incubation with carbachol, PDB or PMA did not cause any modification of the binding of labeled [³H]quinuclidinyl benzilate. In vitro incubation with PDB and PMA produced, as expected, a significant translocation of protein kinase C from the cytosol to the membrane. The incubation of the ciliary muscle with carbachol, using the protocol of exposure that induced maximal desensitization of contractile responses, produced a significant redistribution of the enzyme from the cytosol to the membrane. These findings suggest that agonist-induced modulation of functional cholinergic sensitivity in ciliary muscle is correlated, at least partially, to the translocation of protein kinase C from the cytosol to the membrane. The desensitization by phorbol esters is completely due to protein kinase C activation; during the desensitization process, direct modification of the density and affinity of muscarinic receptors is not involved.     

Effects of endothelin-1 on isolated vascular beds from normotensive and spontaneously hypertensive rats

Endothelin-1 and noradrenaline induced dose-dependent pressor responses in isolated in situ blood perfused mesenteric arterial beds and isolated tail arterial beds of anaesthetised spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). In the tail the sensitivity and maximum to either agonist were the same in SHR and WKY whereas in the mesenteric bed the maximum pressor responses to both agonists were increased in SHR. This effect of endothelin-1 may contribute to the greater increase in blood pressure it induces in anaesthetised SHR compared with WKY.     

Antihypertensive effect of bopindolol on stroke-prone spontaneously hypertensive rats (SHRSP)

The antihypertensive effect of bopindolol, a long-acting beta-adrenoceptor blocking agent, was investigated in stroke-prone spontaneously hypertensive rats (SHRSP). One group received tap water during the period of 8 to 32 weeks of age. The average dose of bopindolol administered was calculated from water intake to be approximately 1.4 mg/kg/day. The lowering effect in blood pressure of bopindolol was apparent at the age of 14 weeks, and this continued up to the end of the experiment. Bopindolol significantly reduced the heart rate. Plasma levels of urea nitrogen (BUN), triglyceride, and phospholipid of SHRSP treated with bopindolol were lower than those of the control SHRSP. One of the 8 control SHRSP died, and no rats treated with bopindolol died during the experiment. The histopathological study revealed that three of the control SHRSP had cerebral apoplexy, whereas there was no evidence of cerebral apoplexy in the treated SHRSP. Chronic treatment of bopindolol clearly alleviated myocardial fibrosis and hypertrophic changes in the left ventricular wall of the heart. Decreases in the incidence of proliferative arteritis and malignant nephrosclerosis in the kidney and necrotizing arteritis of the mesenteric arteries were observed in SHRSP treated with bopindolol. The data presented indicate that bopindolol is a powerful antihypertensive agent.     

阿托伐他汀对自发性高血压大鼠心室重构的影响

目的 :观察阿托伐他汀对自发性高血压大鼠(SHR)心室重构的影响。方法 :2 4只SHR随机分为4组 ,每组 6只。SHR对照组、阿托伐他汀 5 0mg组(5 0mg·kg-1·d-1)、阿托伐他汀 10mg组(10mg·kg-1·d-1)和缬沙坦组 (2 0mg·kg-1·d-1) ;6只Wistar Kyoto大鼠 (WKY)作为正常对照组。灌胃给药共 6周 ,分别于给药前和给药后每 2周测量大鼠尾动脉收缩压 (SBP)。酶法测定血清总胆固醇(TC)、甘油三酯 (TG)、高密度脂蛋白胆固醇 (HDL C)及低密度脂蛋白胆固醇 (LDL C)含量 ,放免法测定血浆和心肌血管紧张素Ⅱ (AngⅡ )水平 ,并检测心肌羟脯氨酸、胶原蛋白含量和全心重量 (HW )、左室重量 (LVM )及左室重量指数 (LVMI)。透射电镜观察心肌超微结构改变。结果 :用药前SHR各组SBP均显著高于WKY正常对照组 (P <0 .0 1) ,给药后第 4、6周 ,阿托伐他汀 5 0mg组SBP明显下降 (P <0 .0 1) ,阿托伐他汀 10mg组不明显 ;缬沙坦组自给药后第 2周 ,SBP明显下降 (P <0 .0 1)。阿托伐他汀5 0mg组TC、TG及LDL C水平较SHR对照组明显降低 (P <0 .0 5或P <0 .0 1) ,阿托伐他汀 10mg组仅LDL C水平明显下降 (P <0 .0 5 )。SHR对照组血浆AngⅡ浓度与WKY正常对照组比较无显著性差异 ,但心肌AngⅡ浓度明显增高 (P <0 .0 5 ) ;给药 6周后 ,阿托伐他