运动对高血压大鼠血浆尾加压素Ⅱ及前列腺素I2的影响

目的:研究运动对自发性高血压大鼠(SHR)血浆尾加压素Ⅱ(UⅡ)的影响。方法:雄性SHR16只,随机分为两组,即安静对照组(8只)和运动组(8只),另正常雄性Wistar大鼠(8只)作为正常对照组。SHR运动组进行8周游泳运动训练。8周后,分别测定3组鼠血浆UⅡ、前列腺素Ⅱ(PGI2)含量。结果:SHR游泳组大鼠血浆UⅡ含量较正常对照组显著性增加[(1.17±0.17)ng/ml∶(1.09±9.77)ng/ml,P0.05],SHR游泳组血压较SHR对照组显著下降[(157.6±7.06)mmHg∶(185.9±6.64)mmHg,P0.01],血浆PGI2含量较SHR对照组患者增加[(183.25±43.46)pg/ml∶(135.43±22.13)pg/ml,P0.01]。结论:适度运动能提高SHR血浆VⅡ、PGI含量,从而使舒血管物质增多,血压下降。     

血管紧张素Ⅱ促高血压大鼠血管平滑肌细胞增殖机制的研究

本工作以培养的正常血压WKY大鼠主动脉平滑肌细胞(ASMC)为对照,探讨血管紧张素Ⅱ(AngⅡ)对培养的SHR ASMC促增殖的机制.结果表明:AngⅡ(10~(-9)～10~(-6)mol/L)对SHR和WKY大鼠的ASMC均有促增殖作用且随剂量增加其作用加强,但对SHR ASMC的促增殖效应明显高于WKY大鼠.应用碱性成纤维细胞生长因子(bFGF)单克隆抗体(A-bFGF)和反义bFGF mR-NA均可明显抑制AngⅡ促SHR ASMC的增殖效应.此外,基础状态下及AngⅡ(10~(-6)mol/L)刺激8h后,SHR ASMC的bFGF基因表达均明显高于WKY大鼠.提示,AngⅡ的促细胞增殖作用部分是通过先诱发bFGF的产生而引起.     

幼龄自发性高血压大鼠血浆尾加压素Ⅱ的变化及负荷运动对它的影响

目的选取幼龄自发性高血压大鼠(SHR)作为研究对象,观察其尚未出现高血压时血浆尾加压素Ⅱ(UⅡ)的变化及负荷运动对它的影响,从而进一步了解UⅡ在遗传性高血压发病中的地位.方法5～6周龄SHR、Wistar-Kyoto大鼠(WKY)各28只随机分为静态组、运动组,静态组行有创血压、血浆UⅡ测定,运动组行游泳负荷运动后做上述指标测定,分别比较静态组WKY、SHR 6min内的平均血压、峰血压、达峰时间、血浆UⅡ的均数和运动组WKY、SHR的上述指标的均数.结果静态组WKY、SHR 6min内的平均血压、峰血压、达峰时间差异有统计学意义(P＜0.05);运动组WKY、SHR平均血压、峰血压、达峰时间差异无统计学意义(P＞0.05).静态组WKY、SHR的血浆UⅡ差异无统计学意义(P＞0.05),运动组WKY、SHR的UⅡ差异有统计学意义(P＜0.05);WKY的血浆UⅡ,运动组较静态组明显升高,差异有统计学意义(P＜0.01);SHR的血浆UⅡ,运动组较静态组比较差异无统计学意义(P＞0.05).结论UⅡ参与了机体应激反应的调节,处于高血压前期的幼龄SHR运动后血浆UⅡ不增高可能是遗传性高血压发生发展的促进因子.     

通心络对自发性高血压大鼠血管内皮功能的影响

目的 观察通心络胶囊对自发性高血压大鼠(SHR)血管内皮功能的保护作用.方法 将24只SHR随机分为通心络组(TXL组)、咪达普利组(MD组)和生理盐水组(SHR组),每组8只.同时还有8只同龄Wistar-Kyoto(WKY)大鼠作为正常对照组.TXL组和MD组分别以通心络胶囊280 mg/(kg·d)和咪达普利0.90 mg/(kg·d)配成2 mL水溶液灌胃4周.SHR组与WKY组灌胃等量生理盐水.实验结束后取血测定内皮素-1(ET-1)、一氧化氮(NO)、血管紧张素Ⅱ(AngⅡ)、丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性.结果 SHR组NO浓度与SOD活性均低于WKY组(P<0.01),TXL组NO浓度与SOD活性则高于SHR组(P<0.01),SHR组ET-1、AngⅡ及MDA水平高于WKY组(P<0.01),TXL组ET-1、AngⅡ及MDA水平均低于SHR组,与MD组比较则无统计学意义(P>0.05).结论 通心络胶囊可能通过增加NO浓度和SOD活性,降低ET-1、AngⅡ及MDA水平,对血管内皮具有保护作用.     

依那普利和氯沙坦对自发性高血压大鼠同型半胱氨酸、环磷酸腺苷水平的影响

目的观察依那普利和氯沙坦降压治疗对自发性高血压大鼠(SHR)血浆同型半胱氨酸(Hcy)、叶酸、维生素B12(VB12)和肾脏血管紧张素Ⅱ(AngⅡ)、环磷酸腺苷(cAMP)水平的影响。方法14w龄雄性SHR分三组。依那普利组15mg/(kg·d)灌胃;氯沙坦组37.5mg/(kg·d)灌胃;SHR对照组及WistarKyoto大鼠(WKY)对照组均以等量蒸馏水灌胃。2w后测定血浆Hcy、叶酸、VB12水平及肾皮质cAMP、AngⅡ含量。结果SHR对照组与WKY对照组相比血浆Hcy、叶酸水平无显著性差异(P>0.05);VB12升高(P<0.05);WKY组及SHR对照组的血压水平与Hcy、VB12水平无显著相关(r=-0.11,P=0.718),血浆Hcy与VB12水平负相关(r=-0.8131,P<0.05);依那普利、氯沙坦对Hcy、叶酸及VB12水平无影响;与SHR对照组相比,依那普利组AngⅡ含量减少(P<0.01);氯沙坦组AngⅡ含量增加(P<0.05);SHR对照组肾皮质cAMP水平低于WKY对照组(P<0.01);依那普利组cAMP显著高于SHR对照组(P<0.01)。结论在满足适量摄入叶酸并且无过量蛋氨酸负荷条件下,Hcy可能没有参与对SHR基础血压的影响;依那普利和氯沙坦对SHR血浆Hcy、叶酸、VB12水平无影响;SHR肾皮质cAMP水平的下降可能并非继发于高血压;依那普利可通过增加SHR肾皮质cAMP水平发挥有益作用。     

依那普利和氯沙坦对自发性高血压大鼠肾皮质环核苷酸水平的影响

目的　观察肾脏环磷酸腺苷 (cAMP)、环磷酸鸟苷 (cGMP)和一氧化氮 (NO)水平与高血压的关系 ,以及依那普利和氯沙坦降压治疗对自发性高血压大鼠 (SHR)肾皮质cAMP、cGMP和NO水平的影响。方法　 14周龄雄性SHR分三组 (n=6) :依那普利组 15mg·kg- 1·d- 1灌胃 ;氯沙坦组 3 7 5mg·kg- 1·d- 1灌胃 ;SHR对照组以等量蒸馏水灌胃。Wistar kyoto(WKY)对照组亦以等量蒸馏水灌胃。采用放射免疫法及Griess法检测肾皮质cAMP、cGMP、血管紧张素Ⅱ (AngⅡ )和NO代谢产物亚硝酸盐 (NO3 - )水平。结果　SHR对照组肾皮质AngⅡ含量较WKY组显著升高 (P <0 0 1) ;与SHR对照组相比 ,依那普利组AngⅡ含量显著降低 (P <0 0 1) ,氯沙坦组AngⅡ含量增加 (P <0 0 5)。与WKY相比 ,SHR对照组cAMP水平低于WKY组 (P <0 0 1) ,依那普利组cAMP水平明显高于SHR对照组 (P <0 0 5) ,氯沙坦组cAMP较SHR对照组有升高趋势 ,但无显著性差异 (P >0 0 5) ;SHR对照组肾皮质NO3 - 、cGMP含量较WKY组显著减少 (P <0 0 1) ;依那普利治疗组NO3- 、cGMP含量较SHR对照组显著增加 (P <0 0 1) ,氯沙坦组与SHR对照组相比 ,NO3 - 、cGMP含量增加(分别为P <0 0 1,P <0 0 5) ,各组NO3- 水平与cGMP水平呈正相关 (r =0 8689,P <0 0 1)。结论　SHR肾     

依那普利和氯沙坦对自发性高血压大鼠肾皮质环核苷酸水平的影响

目的观察肾脏环磷酸腺苷(cAMP)、环磷酸鸟苷(cGMP)和一氧化氮(NO)水平与高血压的关系,以及依那普利和氯沙坦降压治疗对自发性高血压大鼠(SHR)肾皮质cAMP、cGMP和NO水平的影响.方法 14周龄雄性SHR分三组(n=6)依那普利组15 mg*kg-1*d-1灌胃;氯沙坦组37.5 mg*kg-1*d-1灌胃;SHR对照组以等量蒸馏水灌胃.Wistar-kyoto(WKY)对照组亦以等量蒸馏水灌胃.采用放射免疫法及Griess法检测肾皮质cAMP、cGMP、血管紧张素Ⅱ(AngⅡ)和NO代谢产物亚硝酸盐(NO3-)水平.结果 SHR对照组肾皮质Ang Ⅱ含量较WKY组显著升高(P<0.01);与SHR对照组相比,依那普利组Ang Ⅱ含量显著降低(P<0.01),氯沙坦组Ang Ⅱ含量增加(P<0.05).与WKY相比,SHR对照组cAMP水平低于WKY组(P<0.01),依那普利组cAMP水平明显高于SHR对照组(P<0.05),氯沙坦组cAMP较SHR对照组有升高趋势,但无显著性差异(P>0.05);SHR对照组肾皮质NO3-、cGMP含量较WKY组显著减少(P<0.01);依那普利治疗组NO3-、cGMP含量较SHR对照组显著增加(P<0.01),氯沙坦组与SHR对照组相比,NO3-、cGMP含量增加(分别为P<0.01,P<0.05),各组NO3-水平与cGMP水平呈正相关(r=0.8689,P<0.01).结论 SHR肾皮质cAMP、cGMP 显著低于WKY,依那普利和氯沙坦均可升高SHR的cGMP水平,依那普利还可改善SHR肾cAMP代谢.     

依那普利对自发性高血压大鼠心脏局部血管紧张素转换酶及左室肥厚的作用

目的　研究自发性高血压大鼠 (SHR)心脏局部血管紧张素转换酶 (ACE)活性对左室肥厚的影响及依那普利的作用。方法　选用 1 2w龄SHR 40只 ,随机分为两组 ,一组给予依那普利 30mg/ (kg·d)治疗 ,另一组作为对照 ,同时设一同周龄的WKY作为正常对照 ,用病理学图像分析法检测SHR左心室壁厚度、心肌细胞体积比例 (CVF)和心肌血管周围胶原面积和管腔面积比例 (PVCA) ,放免法测定血管紧张素Ⅱ (AngⅡ )浓度 ,荧光法测定ACE活性。结果　 (1 )SHR治疗组 (SHR T)BW/LV与正常对照组 (WKY C)相比无差异 (P >0 0 5) ;(2 )SHR C组AngⅡ浓度为 (5 780± 3 734)ng/mg组织 ,显著高于WKY C组〔(2 72 3± 0 84)ng/mg组织〕(P <0 0 5) ;而依那普利治疗后SHR T组AngⅡ浓度为 (2 757± 2 71 7)ng/mg组织 ,与WKY C组相比无显著差异。 (3)SHR T、SHR C、WKY C三组ACE活性分别为 (0 47± 0 1 2 )单位 / (ml·mg组织 ) ,(0 60± 0 1 3)单位 / (ml·mg组织 ) ,(0 45± 0 1 9)单位 / (ml·mg组织 ) ,SHR T组与SHR C组比较有显著差异 (P <0 0 1 ) ,SHR T组与WKY C组比较无显著差异 (P >0 0 5)。 (4)SHR T组CVF和PVCA分别为 (1 98± 1 57) %和 (0 68± 0 1 9) % ,显著低于SHR C组〔(5 1 1± 2 2 5) % ,(1 2 0± 0     

高血压大鼠心脏肥厚过程中心肌细胞凋亡心肌纤维化动态观察

目的探讨SHR心脏肥厚进展阶段心肌细胞凋亡、心肌纤维化及左室重构特点及其相互关系.方法分别采用末端脱氧核糖核苷酸转移酶介导dUTP缺口末端标记(TUNEL)、放射免疫测定及病理检查方法对16周龄、24周龄、32周龄SHR心肌细胞凋亡指数(APOI)、心肌胶原容积分数(CVF)和心肌血管周围胶原面积(PVCA)、血浆和组织血管紧张素Ⅱ检测,并以同龄Wister大鼠作对照.结果与同龄正常血压Wistar大鼠比较,SHR各周龄组收缩压明显增高、心脏肥厚指标心脏重量(HW)、左室重量(LVW)、左室重量指数(LVW/BW)均显著增加;各周龄组SHR心肌细胞APOI显著增加,各周龄组间无显著性差异;各周龄组SHR大鼠血浆、心肌组织AngⅡ明显增高;24、32周龄SHR的CVF和PVCA显著增加;SHR心肌组织AngⅡ分别与APOI、CVF呈显著正相关,APOI与CVF呈显著正相关.结论心肌细胞凋亡与心肌纤维化参与SHR代偿性心脏肥厚阶段心脏重构病理过程,组织AngⅡ是导致SHR代偿性心脏肥厚阶段心肌细胞凋亡与心肌纤维化的重要机制之一.     

厄贝沙坦和咪达普利抑制自发性高血压大鼠左心室重塑的研究

目的:探讨咪达普利、厄贝沙坦对自发性高血压大鼠(SHR)左心室重塑的抑制作用,并比较二者的作用效果。方法:选用13周龄的SHR30只、Wistar-Kyoto(WKY)大鼠10只,随机分为4组:SHR组,厄贝沙坦组,咪达普利组,WKY组。实验期15周。观察血压、左室重量/体重(LVW/BW)、左室厚度/BW,心肌的形态学(光镜、电镜),血浆、心肌血管紧张素Ⅱ(AngⅡ)及心钠素(ANF)浓度。结果:与SHR组相比,咪达普利组、厄贝沙坦组血压控制良好,LVW/BW、左室厚度/BW均比SHR组小(均P<0.05),血浆、心肌的ANF水平均比SHR组低(均P<0.001),咪达普利组血浆AngⅡ水平低于SHR组,但差异无统计学意义,心肌AngⅡ水平低于SHR组(P<0.05),厄贝沙坦组血浆、心肌AngⅡ水平均明显高于SHR组(均P<0.001),两组心肌结构改变尤其是纤维化均比SHR组减轻,咪达普利组减轻更明显。结论:咪达普利、厄贝沙坦不仅能良好地控制血压,而且可以抑制SHR左心室重塑;在防止心肌和肠系膜动脉结构改变尤其是纤维化方面,咪达普利作用可能优于厄贝沙坦。     

Differential regulation of cardiac adrenomedullin and natriuretic peptide gene expression by AT1 receptor antagonism and ACE inhibition in normotensive and hypertensive rats

OBJECTIVE: To study the effects of long-term treatment with the type 1 angiotensin (AT1) receptor antagonist losartan and the angiotensin-converting enzyme (ACE) inhibitor enalapril, on cardiac adrenomedullin (ADM), atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) gene expression. METHODS: Spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were given losartan (15 mg/kg per day) or enalapril (4 mg/kg per day) orally for 10 weeks. The effects of drugs on systolic blood pressure, cardiac hypertrophy, ANP, BNP and ADM mRNA and immunoreactive-ANP (IR)-ANP, IR-BNP and IR-ADM levels in the left ventricle and atria were compared. RESULTS: Losartan and enalapril treatments completely inhibited the increase of systolic blood pressure occurring with ageing in SHR. The ratio of heart to body weight was reduced in both losartan- and enalapril-treated SHR and WKY rats. Treatment with losartan or enalapril reduced left ventricular ANP mRNA and IR-ANP in both strains, and ventricular BNP mRNA levels in SHR rats. Inhibition of ACE, AT1 receptor antagonism, changes in blood pressure or cardiac mass had no effect on left ventricular ADM gene expression in SHR and WKY rats. In addition, atrial IR-ANP and IR-ADM levels increased in SHR whereas IR-BNP levels decreased in WKY and SHR rats in response to drug treatments. CONCLUSIONS: Our results show that ventricular ADM synthesis is an insensitive marker of changes in haemodynamic load or cardiac hypertrophy. Furthermore, the expression of ADM, ANP and BNP genes is differently regulated both in the left ventricle and atria in response to AT1 receptor antagonism and ACE inhibition.     

厄贝沙坦对SHR左心室肥厚和心肌纤维化的影响

目的 探讨厄贝沙坦对自发性高血压大鼠(SHR)左心室肥厚(LVH)和心肌纤维化的影响。方法 16只16周龄雄性SHR,随机分为厄贝沙坦治疗组和SHR空白对照组;另设同源的WKY大鼠8只为正常对照组。治疗组予厄贝沙坦15 mg/（kg·d）灌胃给药,8周后处死动物,测量左心室心肌厚度并称质量,计算左心室质量/体质量比(LVM/BM);通过Van Gieson染色法观察左心室心肌胶原变化,对左心室心肌胶原容积分数(CVF)和血管周围胶原面积(PVCA)进行定性和半定量分析;HE染色光镜观察左心室心肌病理变化。结果 与WKY组相比,SHR对照组的尾动脉收缩压(SBP)、LVM/BM、左心室壁厚度、CVF、PVCA、均显著增高(P<0.01);与SHR对照组相比,厄贝沙坦治疗组能有效降低SHR的SBP,改善LVH(P<0.01),减少心肌间质及心肌小动脉周围的胶原(P<0.01)。结论 厄贝沙坦可有效降低SHR血压,减轻心肌纤维化和LVH。     

不同时期氯沙坦短暂治疗对自发性高血压大鼠心脏AT1受体、AT2受体表达的影响

目的 观察不同时期氯沙坦短暂治疗对自发性高血压大鼠(SHR)的血压变化及心脏AT1受体、AT2受体表达的影响,探讨血管紧张素Ⅱ 1型受体(AT1R)、血管紧张素Ⅱ2型受体(AT2R)在高血压发病机制中的作用,为早预防、早治疗高血压开辟新的途径.方法 选用4周龄SHR及京都Wistar大鼠(WKY),分成4组:氯沙坦4周...     

氯沙坦、福辛普利对SHR心肌细胞凋亡、心肌纤维化及AngⅡ影响

目的评价氯沙坦、福辛普利对自发性高血压大鼠(SHR)心肌细胞凋亡、心肌纤维化及血管紧张素Ⅱ的效应.方法 16周龄SHR随机分为3组氯沙坦治疗组(SHR-L组)、福辛普利治疗组(SHR-F组)、空白对照组(SHR-C组),每组各10只.分别采用末端脱氧核苷酸转移酶介导dUTP缺口末端标记(TUNEL)、放射免疫及病理检查方法对治疗8周、16周心肌细胞凋亡指数(APOT)、心肌胶原容积分数(CVF)和心肌血管周围胶原面积(PVCA)、血浆和组织血管紧张素Ⅱ检测.结果 (1)与对照组比较,两SHR治疗组8周、16周后收缩压均有明显下降,两组间比较无显著性差异;两治疗组SHR心脏肥厚指标左室重量(LVW)、左室重量指数(LVWI)均有显著性改善,治疗16周后SHR-F组与较SHR-L组LVMI显著性减低;(2)与对照组比较,治疗8周后仅SHR-F组心肌细胞凋亡指数(APOI)显著性下降,治疗16周两治疗组APOI均有显著性下降,尤以SHR-F组下降明显;(3)与对照组比较,治疗8周后SHR-L、SHR-F两组CVF和PVCA有统计学意义下降.治疗16周后与对照组比较,两治疗组CVF和PVCA均显著性下降,其中SHR-F组CVF较SHR-L组下降显著;(4)治疗8周及16周后,SHR-F组心肌组织AngⅡ显著下降, SHR-L组血浆及心肌组织AngⅡ显著增加.结论两药物均能有效逆转心脏肥厚及抗心肌细胞凋亡及心肌纤维化,其中以福辛普利作用显著.两药物上述作用与拮抗心肌组织肾素-血管紧张素-醛固酮系统(RAS)效应有关.     

Alterations in sarcoplasmic reticulum and angiotensin II receptor type 1 gene expression in spontaneously hypertensive rat hearts

Left ventricular hypertrophy (LVH) is an adaptive change in response to hypertensive pressure overload. Some evidence indicates that the decrease in sarcoplasmic reticulum (SR) Ca2+-ATPase mRNA expression, which may contribute to a diastolic dysfunction of the heart, occurs in the experimental pressure overload model. Also, recent studies have demonstrated that angiotensin II (Ang II) and angiotensin II receptor type 1 (AT1) play important roles in LVH. The purpose of this study was to investigate the function of the SR and the role of AT1 in genetic hypertension in spontaneously hypertensive rats (SHR) at ages 10 and 18 weeks. In SHR, cardiac hypertrophy has already developed at 10 weeks of age. SR Ca2+-ATPase activity and mRNA expression were significantly lower in SHR than in Wistar-Kyoto rats (WKY). Plasma renin activity in SHR was unchanged compared with WKY, whereas the Ang II concentration in SHR was significantly higher than that in WKY. AT1 mRNA expression in SHR was similar to that in WKY. These results suggest that in the early stage of hypertension in SHR Ang II may stimulate hypertrophy in the cardiomyocytes through the AT1, which is not downregulated by a high concentration of Ang II.     

血管紧张素Ⅱ及其受体拮抗剂对心肌细胞肥大的影响

目的观察血管紧张素Ⅱ（AngⅡ）、AT1受体拮抗剂氯沙坦和AT2受体拮抗剂PD123177对心肌细胞蛋白质合成速率和AT1受体mRNA表达的影响。方法采用3H-亮氨酸掺入法测定培养的心肌细胞蛋白质合成速率,RT-PCR方法检测心肌细胞AT1受体mRNA表达。结果在培养的心肌细胞中加入AngⅡ可明显增加心肌细胞3H-亮氨酸的掺入量,并呈剂量依赖性,氯沙坦可显著抑制AngⅡ引起的蛋白质合成增加,而PD123177对其无影响;AngⅡ上调AT1受体基因表达,氯沙坦抑制其上调,PD123177无影响。结论AngⅡ可通过上调AT1受体引起心肌细胞肥大,氯沙坦下调AT1受体,抑制心肌细胞肥大。     

The Mechanism of Distinct Diurnal Variations of Renin-Angiotensin System in Aorta and Heart of Spontaneously Hypertensive Rats

Diurnal variations in plasminogen activator inhibitor-1 mRNA expression are different between the spontaneously hypertensive rats (SHRs) and the Wistar-Kyoto (WKY) rats, and between the aorta and the heart. To elucidate the mechanisms, we examined diurnal changes in the circulating renin-angiotensin system in the SHR and WKY rats. Diurnal variations in plasma renin activity (PRA), plasma angiotensin I, and aldosterone concentrations were similar between the SHR and WKY rats. On the other hand, plasma angiotensin II (Ang II) concentration in the SHR was lower than that in the WKY rats at most time points, but increased to the level of the WKY rats in the late light phase. Treatment with AT1 receptor antagonist candesartan increased plasma Ang II concentration except at ZT 8 and lessened its diurnal variation in the SHR. At the peak in plasma Ang II in the SHR, Ang II regulated genes such as transforming growth factor-β1 and p22phox were upregulated in the aorta. On the other hand, these genes were upregulated throughout the day in the heart of SHR. Candesartan treatment increased AT1a receptor mRNA expression in the heart but not in the aorta of SHR. These findings suggest that an AT1 receptor-mediated mechanism might cause a surge in plasma Ang II concentration at the late light phase in the SHR. Homologous down-regulation of AT1a receptor by Ang II may dampen the effect of a surge in plasma Ang II concentration in the heart of SHR.     

Upregulation of interleukin-8/CXCL8 in vascular smooth muscle cells from spontaneously hypertensive rats.

Chemokines promote vascular inflammation and play a pathogenic role in the development and maintenance of hypertension. In the present study, the expression of the chemokine interleukin-8/CXCL8 (IL-8/CXCL8) was investigated in cultured vascular smooth muscle cells (VSMC) obtained from the thoracic aorta of spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). IL-8/CXCL8 expression in thoracic aorta tissue and VSMC in SHR were significantly higher than in WKY. However, the expression of CXCR1 mRNA in VSMC from WKY was higher than that in VSMC from SHR. Angiotensin II (Ang II) induced a higher level of IL-8/CXCL8 mRNA expression in VSMC from SHR than in VSMC from WKY. The time course of Ang II-induced IL-8/CXCL8 expression in VSMC from SHR correlated with those of Ang II-induced CXCL1 and Ang II type 1 (AT1) receptor expression, and the expression of IL-8/CXCL8 by Ang II was inhibited by the AT1 receptor antagonist losartan. The effect of Ang II on IL-8/CXCL8 expression was not dependent on nuclear factor-kappaB (NF-kappaB) activation, but was mediated by an extracellular signal-regulated kinase (ERK) signaling pathway. Although Ang II directly induced IL-8/CXCL8 expression, expression of Ang II-induced IL-8/CXCL8 decreased in VSMC transfected with heme oxygenase-1. These results suggest that IL-8/CXCL8 plays an important role in the pathogenesis of Ang II-induced hypertension and vascular lesions in SHR.     

Prolonged QT interval is associated with blood pressure rather than left ventricular mass in spontaneously hypertensive rats

QT interval is prolonged in hypertensive individuals, although the factors responsible for this increase are not completely understood. We questioned whether enhanced left ventricular mass (LVM) or increased systemic blood pressure represents the principal factor determining QT prolongation in the period of development of hypertension and left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR). In 12-and 20-week-old SHR (SHR12 and SHR20) and age-matched normotensive Wistar-Kyoto rats (WKY12 and WKY20), arterial systolic blood pressure (sBP) was measured using tail-cuff technique. Orthogonal Frank ECG was registered in anaesthetized animals in vivo, and bipolar ECG was measured in spontaneously beating isolated hearts in vitro. Progressive increase of sBP and LVM resulted in significant QT prolongation in SHR20 as compared to WKY12, WKY20, and also to SHR12 in vivo (WKY12: 82 +/- 9 ms, WKY20: 81 +/- 9 ms, SHR12: 88 +/- 15 and SHR20: 100 +/- 10, respectively; p < 0.05) but not in isolated hearts (WKY20: 196 +/- 39 ms and SHR20: 220 +/- 55, respectively; NS). In whole animals, QT duration was positively related to sBP (r = 0.6842; p < 0.001) but not to LVM (r = 0.1632, NS) in SHR20. The results suggest that QT prolongation in SHR developing hypertension and LVH depends on blood pressure rather than increase in LVM. In this period, myocardial hypertrophy is probably the predisposition for QT prolongation, but the significant change manifests only in the presence of elevated systemic factors.