卡托普利治疗后2K1C肾性高血压大鼠心脏和主动脉Gαq/11介导的信号转导通路的变化

目的研究Gαq/11介导的信号转导通路在2K1C肾性高血压大鼠心脏和主动脉中的变化以及卡托普利治疗对其的影响. 方法制备2K1C肾性高血压大鼠模型, 于术后4～8周给予卡托普利(150 mg/kg),观察尾动脉收缩压、左室重与体重之比和主动脉形态学改变.测定心脏和主动脉中Gαq/11含量和磷脂酶C(PLC)活性. 结果 2K1C肾性高血压大鼠在术后4周和8周出现明显的高血压、心肌肥大和主动脉增厚, 心脏和主动脉中Gαq/11含量明显增加.卡托普利治疗4周可以降低血压并逆转心肌肥大, 心脏Gαq/11含量及PLC活性分别降低了15.8%和30.9%, 而主动脉中Gαq/11含量及PLC活性均无变化. 结论 Gαq/11介导的信号转导通路参与2K1C肾性高血压的发生和维持.卡托普利可以逆转心肌肥大, 这一作用可能是通过抑制血管紧张素Ⅱ(Ang Ⅱ)的生成从而消除 Ang Ⅱ导致的Gαq/11介导的信号转导通路的激活而实现的.     

血压平逆转二肾一夹肾性高血压大鼠左室重构的作用及机制的研究

目的研究血压平逆转二肾一夹(2K1C)肾性高血压大鼠左室重构的作用及其机理.方法建立2K1C肾性高血压大鼠(RHR)模型,随机分为血压平大剂量组[73.00 g/(kg*d)];血压平中剂量组[36.50 g/(kg*d)];血压平小剂量组[18.25 g/(kg*d)];依那普利组[10 mg/(kg*d)];模型组及假手术对照组.左室及室间隔称重(LVW),计算左室重量指数(LVW/BW)之比,测量心肌细胞形态参数及原癌基因C-myc和C-fos表达阳性细胞的平均光密度值.结果血压平降低血压,LVW、LVW/BW、心肌细胞体积及血清PCⅢ含量,抑制原癌基因C-myc和C-fos的表达,血压平大、中剂量组LVW、LVW/BW及血清PCⅢ含量明显低于模型组(P<0.01),图像分析心肌细胞形态参数(面积、周长、平均直径、长径及短径)及C-myc、C-fos表达阳性的心肌细胞平均光密度值明显低于模型组(P<0.01),与假手术组接近(P＞0.05).结论复方中药血压平具有逆转2K1C肾性高血压大鼠左室重构的作用,降低血压,降低血清PCⅢ含量,抑制Ⅲ型胶原合成,防治心肌纤维化及降低原癌基因C-myc和C-fos的表达,抑制心肌细胞肥大,减轻左心室肥厚,是其逆转二肾一夹肾性高血压大鼠左室重构的部分机制.     

牛磺酸对肾性高血压大鼠血浆及心肌血管紧张素Ⅱ、醛固酮的影响

目的　观察牛磺酸 (Tau)对肾性高血压大鼠血浆及心肌血管紧张素 (Ang )、醛固酮 (Ald)的影响。方法　Wistar大鼠随机分为假手术组 (Sham组 )、二肾一夹肾性高血压模型组 (2 K1C组 )、Tau治疗组 (2 K1C+Tau组 ) ,每组 8只。测定并比较各组尾动脉收缩压 (SBP)、左心室重量指数 (L VWI)、心肌胶原含量、心肌纤维直径、血浆及心肌 Ang 、Ald含量。结果　 2 K1C组大鼠 SBP、L VWI、心肌胶原含量、心肌纤维直径、血浆及心肌 Ang 、Ald含量较 Sham组显著增加 (P<0 .0 1)。牛磺酸 (5 0 mg/ kg· d)治疗 8周显著降低 2 K1C大鼠 SBP、L VWI、心肌胶原含量、心肌纤维直径、血浆及心肌 Ang 和 Ald含量 (P<0 .0 1)。结论　牛磺酸可降低肾性高血压大鼠循环及心肌局部肾素血管紧张素醛固酮系统 (RAAS)活性 ,抑制心肌细胞肥大及胶原增生 ,有效防治左室肥厚     

螺内酯抗CaN依赖的肾性高血压大鼠心肌肥大的研究

目的观察螺内酯(Spironolactone,Spiro)抗钙调神经磷酸酶(calcineurin,CaN)依赖的肾性高血压大鼠心肌肥大的作用.方法20只Wistar大鼠随机分为3组两组采用一肾一夹模型制造肾性高血压,其中spiro组(n=7)给予螺内酯灌胃,op组(n=7)予水灌胃;假手术组(sham op n=6)只给予水灌胃.称重法测定心重比,发色底物法测CaN活性;同时用免疫组织化学染色方法,观察心肌中CaN及活化T细胞核因子(nuclear factor of activatedT cell,NFAT)的表达.结果肾性高血压大鼠经螺内酯灌胃4周,其心重比较未干预组明显降低(P＜0.05),心肌肥大受到抑制,同时发现心肌中CaN活性较未干预组显著下降,免疫组化显示螺内酯干预组心肌中CaN及NFAT表达降低.结论螺内酯抑制肾性高血压心肌肥大的机制与其下调心肌胞浆中CaN表达及其活性有关.     

β1受体反义基因治疗对两肾一夹高血压大鼠心肌Bcl-2的影响

目的比较两肾一夹(2K1C)肾性高血压大鼠心肌Bcl-2的表达,探讨阳离子脂质体混合物介导的β1受体反义基因治疗对肾性高血压大鼠血压及心肌Bcl-2表达的影响.方法将18只雄性SD大鼠随机分成3组,每组6只.其中2组12只用来制作两肾一夹高血压模型,作为两肾一夹组;6只作为假手术组,仅分离左肾动脉而不套银夹.两肾一夹模型又分为反义寡核苷酸(β1-AS-ODN)组(反义组)和反向寡核苷酸(Inverted ODN,β1-IN-ODN)组(反向组).阳离子脂质体1,2-bis(oleoyloxy)-3-(trimethylammonio)propane/cholesterol(DOTAP)和辅助脂质体l-a-dioleoyl hosphatidylethanolamine(DOPE)以11的摩尔比混合.阳离子脂质体混合物(DOTAP/DOPE)与β1-AS-ODN、β1-IN-ODN混合的摩尔比率均为2.0,经鼠尾静脉注射.监测血压,8周后测定血流动力学指标,免疫组织化学方法检测3组大鼠心肌Bcl-2的表达.结果反义寡核苷酸治疗可使血压显著下降,单剂治疗可维持血压降低27 d,血压最大下降39mm Hg.反义组的心脏湿重/体重(HW/BW)也显著低于对照组(P<0.01).两肾一夹组心肌Bcl 2表达明显高于假手术组,β1-IN-ODN组心肌Bcl-2表达明显高于β1-AS-ODN组.结论以β1受体为靶基因的反义基因对肾性高血压有效,单剂治疗降压持续时间长,而且在抑制血压和左室肥厚的同时也明显抑制心肌Bcl-2的表达,提示β1-AS-ODN对心肌Bcl-2的抑制在抗高血压靶器官损伤过程中起一定的作用.     

缬沙坦对肾性高血压大鼠心肌肥厚及富脯氨酸蛋白酪氨酸激酶表达的影响

背景和目的 富脯氨酸蛋白酪氨酸激酶(Pyk2)是一种新发现且活跃的酪氨酸蛋白激酶,该酶能催化多种含SH同源域2的底物蛋白磷酸化,参与细胞的生长、增殖和分化.本文以肾性高血压大鼠(RHR)为模型,研究心肌中Pyk2的表达情况,探讨缬沙坦逆转左室重构的可能机制.方法 制备两肾一夹肾性高血压大鼠模型;将大鼠随机分为假手术组、模型组和缬沙坦组[术后第29天给予缬沙坦30 mg/(kg·d)];分别于术前及术后第1、4、8和12周测定动脉血压和心肌肥厚指数,用免疫印迹法检测心肌组织中Pyk2及其磷酸化表达.结果 术后4周已发生心肌肥大,8～12周心肌肥大进一步加重,缬沙坦能显著降低肾性高血压大鼠的血压,并能有效抑制心肌肥厚的形成(P＜0.01);术后大鼠心肌组织Pyk2活性逐渐增加(1周时,P＜0.05,4、8、12周时P＜0.01);缬沙坦降低Pyk2及其磷酸化表达水平,与同周龄模型组相比差异有非常显著意义(P＜0.01).结论 Pyk2及磷酸化在RHR心肌组织内表达增高,且与心肌肥厚相关;缬沙坦能下调Pyk2的表达和磷酸化变化.这可能是血管紧张素Ⅱ受体拮抗剂逆转心肌肥厚重构的机制之一.     

环孢霉素A抑制肾性高血压大鼠心肌肥大的作用机制

目的观察环孢霉素A对肾性高血压大鼠心肌肥大的抑制作用,并探讨其作用机制.方法 20只Wistar大鼠随机分为3组两组采用一肾一夹模型制造肾性高血压,其中高血压组(n=7)予生理盐水腹腔注射;CsA组(n=7)给予环孢霉素A(CsA)5 mg·kg-1·d-1腹腔注射;假手术组(n=6)只给予生理盐水腹腔注射.称重法测定心重比,发色底物法测CaN活性;半定量PCR测定各组心肌组织中心房利钠因子(ANF)及CaNmRNA的水平,同时用免疫组织化学染色方法,观察心肌中CaN及活化T细胞核因子(nuclearfactor of activated T cell,NFAT)的表达.结果肾性高血压大鼠经CsA干预4周,其心重比较未干预组明显降低(P＜0.05),ANF mRNA水平较手术组明显降低(P＜0.05),与假手术组水平接近,心肌肥大受到抑制,同时发现心肌中CaN活性较未干预组显著下降,CaN mRNA水平较手术组明显降低(P＜0.05),免疫组化显示CsA干预组心肌中CaN及NFAT表达降低.结论 CsA抑制肾性高血压心肌肥大的机制与其下调心肌胞浆中CaN表达及其活性有关.     

卡托普利治疗后2K1C肾性高血压大鼠心脏和主动脉Gαq/11介导的信号转导通路的变化(英文)

目的　研究Gαq/ 11介导的信号转导通路在 2K1C肾性高血压大鼠心脏和主动脉中的变化以及卡托普利治疗对其的影响。方法　制备 2K1C肾性高血压大鼠模型 ,于术后 4～ 8周给予卡托普利 (15 0mg/kg) ,观察尾动脉收缩压、左室重与体重之比和主动脉形态学改变。测定心脏和主动脉中Gαq/ 11含量和磷脂酶C(PLC)活性。结果　 2K1C肾性高血压大鼠在术后 4周和 8周出现明显的高血压、心肌肥大和主动脉增厚 ,心脏和主动脉中Gαq/ 11含量明显增加。卡托普利治疗 4周可以降低血压并逆转心肌肥大 ,心脏Gαq/ 11含量及PLC活性分别降低了 15 .8%和 30 9% ,而主动脉中Gαq/ 11含量及PLC活性均无变化。结论　Gαq/ 11介导的信号转导通路参与 2K1C肾性高血压的发生和维持。卡托普利可以逆转心肌肥大 ,这一作用可能是通过抑制血管紧张素Ⅱ (AngⅡ )的生成从而消除AngⅡ导致的Gαq/ 11介导的信号转导通路的激活而实现的     

异莲心碱防止高血压大鼠左室肥厚的可能机制

背景 既往报告异莲心碱是从莲子心中分离的一种双苄基喹啉生物碱单体,具有抗心律失常、Ca2 拮抗及阻断α受体作用,对高血压左室肥厚有不同程度的改善.高血压左室肥厚心肌肌浆网钙泵(SERCA)活力较正常心肌降低.目的 探讨异莲心碱对高血压大鼠左室肥厚及SERCA活力的影响.方法 将二肾一夹肾血管性高血压大鼠(RHR)模型,随机分为3组:正常对照组、肾血管性高血压大鼠对照组(未治疗RHR组)和异莲心碱治疗组.在异莲心碱治疗组持续给药10周后,分别测定各组大鼠的血压、左室质量/体质量,以及左室心肌SERCA活力.结果 治疗后,异莲心碱治疗组血压(136.4±14.6)mm Hg较未治疗RHR组(189.8±4.4)mm Hg显著降低(P＜0.01);异莲心碱治疗组左室质量/体质量(2.23±0.43)也较未治疗RHR组(2.93±0.52)显著降低(P＜0.05);异莲心碱治疗组左室心肌SERCA活力[(0.91±0.18)μmol/(g protein·min)]较未治疗RHR组[(0.61±0.23)μmol/(g protein·min)]显著升高(P＜0.05),但仍较正常对照组[(1.32±0.18)μmol/(g protein·min)]低(P＜0.01).结论 异莲心碱能降低RHR的血压,减低RHR的左室质量/体质量,对高血压左室肥厚具有一定的防治作用;其机制可能与异莲心碱能升高RHR肥厚心肌肌浆网SERCA活力,改善心肌细胞内钙超载有关.     

缬沙坦对肾性高血压大鼠心肌肥厚及富脯氨酸蛋白酪氨酸激酶表达的影响

背景和目的富脯氨酸蛋白酪氨酸激酶(Pyk2)是一种新发现且活跃的酪氨酸蛋白激酶,该酶能催化多种含 SH 同源域2的底物蛋白磷酸化,参与细胞的生长、增殖和分化。本文以肾性高血压大鼠(RHR)为模型,研究心肌中 Pyk2的表达情况,探讨缬沙坦逆转左室重构的可能机制。方法制备两肾一夹肾性高血压大鼠模型;将大鼠随机分为假手术组、模型组和缬沙坦组[术后第29天给予缬沙坦30 mg/(kg·d)];分别于术前及术后第1、4、8和12周测定动脉血压和心肌肥厚指数,用免疫印迹法检测心肌组织中 Pyk2及其磷酸化表达。结果术后4周已发生心肌肥大,8～12周心肌肥大进一步加重,缬沙坦能显著降低肾性高血压大鼠的血压,并能有效抑制心肌肥厚的形成(P<0.01);术后大鼠心肌组织 Pyk2活性逐渐增加(1周时,P<0.05,4、8、12周时 P<0.01);缬沙坦降低Pyk2及其磷酸化表达水平,与同周龄模型组相比差异有非常显著意义(P<0.01)。结论 Pyk2及磷酸化在 RHR心肌绀织内表达增高,且与心肌肥厚相关;缬沙坦能下调 Pyk2的表达和磷酸化变化。这可能是血管紧张素Ⅱ受体拮抗剂逆转心肌肥厚重构的机制之一。     

Treatment with the arginase inhibitor N(omega)-hydroxy-nor-L-arginine improves vascular function and lowers blood pressure in adult spontaneously hypertensive rat

OBJECTIVE: High vascular arginase activity and subsequent reduction in vascular nitric oxide production were recently reported in animal models of hypertension. The present study investigated the effects of in-vivo arginase inhibition on blood pressure and vascular function in adult spontaneously hypertensive rats. METHODS: Ten-week-old spontaneously hypertensive rats and normotensive age-matched Wistar-Kyoto rats were treated with or without the selective arginase inhibitor N-hydroxy-nor-L-arginine for 3 weeks (10 or 40 mg/kg per day, intraperitoneally). Systolic blood pressure and cardiac rate were measured before and during treatment. Flow and pressure-dependent reactivity as well as remodeling of mesenteric arteries, acetylcholine-dependent vasodilation of aortic rings, cardiac hypertrophy, arginase activity and nitric oxide production were investigated in 13-week-old spontaneously hypertensive rats. RESULTS: In spontaneously hypertensive rats, N-hydroxy-nor-L-arginine treatment decreased arginase activity (30-40%), reduced blood pressure ( approximately 35 mmHg) and improved the reactivity of mesenteric vessels. However, vascular and cardiac remodeling was not different between treated and untreated spontaneously hypertensive rats. In Wistar-Kyoto rats, N-hydroxy-nor-L-arginine did not affect blood pressure. Finally, arginase inhibition was associated with increased nitric oxide production. Consistent with this, the response of aortic rings to acetylcholine was fully restored by N-hydroxy-nor-L-arginine, and the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester significantly reduced the effect of N-hydroxy-nor-L-arginine on flow-dependent vasodilation. CONCLUSION: Pharmacological inhibition of arginase in adult spontaneously hypertensive rats decreases blood pressure and improves the reactivity of resistance vessels. These data represent in-vivo argument in favor of selective arginase inhibition as a new therapeutic strategy against hypertension.     

Quantification of the contribution of cardiac and arterial remodeling to hypertension

The study aim was to quantify the individual and combined contributions of both the arterial system and the heart to systolic blood pressure in hypertension. We assessed the parameters of a heart-arterial model for normotensive control subjects and hypertensive patients with left ventricular adaptation patterns classified as normal, concentric remodeling, concentric hypertrophy, or eccentric hypertrophy. The present simulations show that vascular stiffening alone increases the pulse pressure without increasing systolic blood pressure. It is only in combination with an increased peripheral resistance that arterial stiffening leads to systolic hypertension in concentric remodeling and concentric hypertrophy. The contribution of cardiac pump function to the increase in blood pressure depends on cardiac remodeling, hypertrophy, or both. In hypertensive patients with a normal left ventricle, the heart is responsible for 55% of the increase in systolic blood pressure. In concentric remodeling, concentric hypertrophy, and eccentric hypertrophy, the cardiac contribution to the increase in systolic blood pressure is 21%, 65%, and 108%, respectively. We conclude that along with arterial changes, cardiac remodeling and hypertrophy contribute to hypertension.     

Role of blood pressure reduction in prevention of cardiac and vascular hypertrophy

We investigated whether prevention of cardiac and vascular remodeling associated with inhibition of angiotensin II is independent of the blood pressure (BP)-lowering action of angiotensin II type 1 (AT1) receptor blockade. Spontaneously hypertensive rats, 8 weeks old, were treated with olmesartan, atenolol, or vehicle in their drinking water for 56 days. At the end of each treatment, arterial pressure and heart rate were measured, the ratio of heart weight to body weight was calculated, collagen deposition in the heart was determined histochemically using picrosirius red staining, and wall-to-lumen ratio in isolated mesenteric arteries was measured by a videographic approach. At 3 weeks after the initiation of treatment, rats medicated with olmesartan showed lower values of systolic BP compared with rats given atenolol or vehicle, whereas no difference in directly measured BP were observed at the end of study in anesthetized rats given olmesartan or atenolol. Rats given atenolol showed sustained bradycardia, whereas cardiac hypertrophy and collagen deposition was prevented only in spontaneously hypertensive rats given olmesartan. Olmesartan or atenolol reduced arteriolar wall-to-lumen ratio (olmesartan: 11.5+/-0.4%; atenolol: 13.3+/-0.6%; vehicle: 18.4%+/-1.1); however, this effect was greatest in rats medicated with the angiotensin II type 1 antagonist. Although control of BP is a factor in the prevention of cardiac and vascular hypertrophy, our studies suggest that blockade of angiotensin II receptors may attenuate the structural changes in the heart and blood vessels of hypertensive animals independent of a reduction in BP.     

Vascular and cardiac effects of grape powder in the spontaneously hypertensive rat

BackgroundWe previously reported that resveratrol, a polyphenol found in red grapes, attenuated changes in small artery geometry and stiffness, as well as cardiac hypertrophy and cardiac function in the spontaneously hypertensive rat (SHR). However, in addition to resveratrol, grapes contain a variety of bioactive polyphenols such as catechins, anthocyanins, and flavonoids. Therefore, we investigated the effects of grape consumption in SHR.MethodsWistar-Kyoto (WKY) rats and SHR were treated with freeze-dried grape powder for 10 weeks. Dilatory, geometry, and stiffness properties of mesenteric small arteries were assessed by pressurized myography. Left ventricular mass index and cardiac function were assessed by two-dimensional guided M-mode and pulse-wave Doppler echocardiography.ResultsElevated blood pressure in SHR was associated with remodeling and impaired endothelium-dependent relaxation of small arteries. Augmented left ventricular mass index (reflecting hypertrophy) and diminished cardiac function were also evident in SHR. Although grape treatment failed to affect cardiac dysfunction, it elicited a significant reduction in blood pressure, improved arterial relaxation, increased vascular compliance, and attenuated cardiac hypertrophy.ConclusionsTreatment with whole grape powder conferred mild vascular and cardiac benefits in SHR. Therefore, dietary grape consumption may be a feasible and salutary adjunct to pharmacological treatment of human hypertension.American Journal of Hypertension 2012; doi:10.1038/ajh.2012.98.     

Cardiac hypertrophy in early hypertension.

Studies of cardiac hypertrophy in spontaneously hypertensive rats have indicated that left ventricular hypertrophy occurred even in the prehypertensive stage. These findings suggested that other factors besides blood pressure levels, and including possibly a genetic predisposition to myocardial hypertrophy, could play a role in structural cardiovascular alterations in spontaneously hypertensive rats. More recent studies have confirmed these anatomic results; left ventricular hypertrophy was vectorcardiographically detected even in the prehypertensive stage in voth young stroke-prone rats and stroke-resistant spontaneously hypertensive rats. Further, a close relation was found between degree of left ventricular hypertrophy and vascular hypertrophy or hyperplasia; this suggests that early detection of left ventricular hypertrophy may be a useful indicator of the incipient stage of structural vascular changes in genetic hypertension.     

Blood flow regulates the development of vascular hypertrophy, smooth muscle cell proliferation, and endothelial cell nitric oxide synthase in hypertension

Blood flow participates in vascular remodeling during development and growth by regulating cell apoptosis and proliferation. However, its significance in the development of vascular hypertrophy and vascular remodeling in hypertensive patients is not known. We investigated how changing blood flow through the common carotid artery (CA) of young adult rats rendered hypertensive via aortic coarctation affects CA hypertrophy and/or remodeling responses to hypertension. Blood flow was reduced by approximately 50% as a result of ligation of the external CA immediately after hypertension was induced, and the effects of that procedure were compared with those in similarly treated normotensive rats. Reducing blood flow in the hypertensive animals markedly augmented the development of CA hypertrophy over the ensuing 14 days by increasing the vessel wall cross-sectional area. In those animals, CA lumen size was unaltered by reducing blood flow, as was CA structure in normotensive animals. The greater hypertrophy in the hypertensive animals with reduced blood flow was associated with enhanced smooth muscle cell (SMC) proliferation 3 days after the hemodynamic changes were induced. There also appeared to be more extensive remodeling of the endothelium in the hypertensive animals with normal flow; this was indicated by the greater frequency of apoptotic endothelial cells at that time. This reduction in blood flow also attenuated endothelial cell nitric oxide synthase expression in hypertensive animals but not in normotensive animals. Severe reductions in blood flow ( approximately 90%) were required to reduce endothelial cell nitric oxide synthase in the normotensive animals. Increasing CA nitric oxide levels by perivascular application of S-nitroso-N-acetylpenicillamine (SNAP) to the CAs of hypertensive animals with reduced endothelial cell nitric oxide synthase attenuated the greater SMC proliferation. Thus, reduced blood flow in hypertensive animals promotes hypertrophy by enhancing SMC proliferation via mechanisms that reduce the inhibitory effects of nitric oxide on SMC proliferation.     

Abnormal polyamine metabolism in hypertensive cardiac hypertrophy

In order to assess myocardial hypertrophic activity during the process of hypertensive cardiac hypertrophy in the presence and absence of treatment with anti-hypertensive agents, we analyzed myocardial polyamine concentrations in spontaneous hypertensive (SHR) rats and control rats of Wistar Kyoto (WKY) strain. The anti-hypertensive agents studied were diltiazem, hydralazine and captopril, each of which was administered for 5 weeks. In comparison with WKY rats, SHR rats showed elevated blood pressure and enlarged hearts with higher myocardial spermidine concentration. Although blood pressure was lowered in the diltiazem-treated SHR rats, heart weight and myocardial spermidine concentration increased as in untreated SHR rats. In the hydralazine-treated group increases in both blood pressure and myocardial spermidine concentration were suppressed, while an increase in heart weight was not. In the captopril-treated group, increases in blood pressure, heart weight and spermidine concentration were all suppressed. Since spermidine level appears to be a sensitive indicator of hypertrophic activity in the heart, this study suggests that captopril exerts an inhibitory effect on hypertensive cardiac hypertrophy whereas diltiazem does not. It also suggests that hypertrophy may reach a certain plateau level earlier in the hydralazine-treated animals than in others.     

Hypertrophy in the denervated heart: a comparison of central sympatholytic treatment with 6-hydroxydopamine and peripheral sympathectomy with nerve growth factor antiserum.

The effects of widespread destruction of central catecholaminergic structures on systemic hemodynamics, ventricular performance, myocardial hypertrophy and the renin-angiotensin system in developing male spontaneously hypertensive rats of the Okamoto strain (SHR) and control normotensive Kyoto Wistar (WKY) rats were examined and contrasted with the effects of peripheral sympathectomy. Both centrally administered 6-hydroxydopamine (6-OHDA) and nerve growth factor antiserum (NGFAS) prevented the development of hypertension in the spontaneously hypertensive rats but did not affect blood pressure in the control rats. Peripheral vascular resistance remained elevated and cardiac and stroke indexes depressed in both 6-OHDA- and NGFAS-treated spontaneously hypertensive rats despite preservation of normal blood pressure. Ventricular performance was depressed in the sham-treated spontaneously hypertensive rats and was not improved by either treatment. Neither 6-OHDA nor NGFAS treatment prevented the development of left ventricular hypertrophy in the spontaneously hypertensive rats despite the decrease in blood pressure. Plasma renin activity was elevated in the 6-OHDA-treated spontaneously hypertensive rats compared with the sham-treated spontaneously hypertensive control rats but was unaffected by treatment with NGFAS.The data indicate that destruction of central and peripheral noradrenergic structures in the immature spontaneously hypertensive rats prevents the development of hypertension by different physiologic mechanisms but does not alter the suppressed ventricular function, the increased peripheral resistance or the development of myocardial hypertrophy. These results support the concept that increased sympathetic activity is necessary for the development of hypertension in spontaneously hypertensive rats but not for the development of myocardial dysfunction or hypertrophy.     

Effect of treatment with lercanidipine on heart of Cohen-Rosenthal diabetic hypertensive rats

The influence of treatment with the dihydropyridine-type Ca2+ antagonist lercanidipine on heart and coronary microanatomic changes was investigated in spontaneously hypertensive rats, Cohen-diabetic rats, and Cohen-Rosenthal diabetic hypertensive rats. At 12 weeks of age, animals were left untreated (control groups) or were treated for 8 weeks with an oral dose of 3 mg/kg per day of lercanidipine. Wistar-Kyoto rats were used as a normotensive reference group. In spontaneously hypertensive rats and diabetic hypertensive rats, systolic blood pressure was higher in comparison with Wistar-Kyoto rats. Augmented pressure values were decreased by lercanidipine treatment. Systolic blood pressure was slightly higher in Cohen-diabetic rats than in Wistar-Kyoto rats, and this increase was countered by treatment with lercanidipine. In spontaneously hypertensive rats, diabetic rats, and diabetic hypertensive rats, the thickness of left ventricle and cardiocyte area were increased. Focal connective tissue areas and diffuse accumulation of connective tissue were observed in the left ventricle of spontaneously hypertensive and Cohen-diabetic rats, respectively. Pharmacological treatment countered left ventricle thickening and restored cardiocyte area values in subendocardium. An increased thickness of tunica media accompanied by luminal narrowing was found in coronary artery branches of control spontaneously hypertensive and diabetic hypertensive rats. Treatment with lercanidipine countered vascular changes primarily in small-sized coronary arteries. These results indicate that hypertensive, diabetic, and diabetic hypertensive rats undergo cardiac hypertrophy and vascular changes affecting small-sized coronary arteries. Treatment with lercanidipine countered hypertension-related cardiac and coronary changes, suggesting that this dihydropyridine-type Ca2+ antagonist may improve heart and coronary structure in diabetes associated with hypertension.     

Hemodynamic consequences of left ventricular hypertrophy in spontaneously hypertensive rats.

Compared with hearts from normotensive rats isolated, perfused hearts from spontaneously hypertensive rats exhibit a rightward shift of the Frank-Starling curve in the lower range of filling pressures, that is, up to 10 mm Hg. The extent of this shift is proportional to the degree of left ventricular hypertrophy. This is suggested to be a consequence of an altered relation between end-diastolic pressure and end-diastolic tension of the progressively more thick-walled left ventricle. Furthermore, the cardiac function curves revealed that maximal cardiac performance is apparently better in spontaneously hypertensive rats than in normotensive rats at increased levels of afterload. Therefore, left ventricular hypertrophy in established hypertension seems to contribute to adjustment of cardiac performance to the enhanced pressure work in hypertension; however, this occurs at the expense of a rightward shift of the Frank-Starling curve. In spontaneously hypertensive rats studied in vitro, coronary vascular resistance per unit weight of tissue was increased at maximal dilation, as was maximal pressor response. This may reflect the same type of structural vascular adaptation that occurs in most systemic vascular beds in hypertension and that contributes to maintenance of increased vascular reactivity and flow resistance in both hypertensive patients and spontaneously hypertensive rats. Apparently as a consequence of this adaptation, splanchnic nerve stimulation at an increasing rate caused exaggerated increases in resistance in anesthetized hypertensive rats by comparison with findings in normotensive rats. However, the effect of capacitance vessel constriction on stroke volume caused by splanchnic nerve stimulation was less pronounced in hypertensive rats. This relative “hyporeactivity” of the capacitance vessels also suggests an altered relation between cardiac filling pressure and stroke volume of the hypertrophied left ventricle in the spontaneously hypertensive rat.