尿促皮素诱导乳大鼠心肌细胞肥大的作用及信号传导机制

目的探讨尿促皮素(urocortin)诱导大鼠心肌细胞肥大的作用及其信号传导机制。方法实验分8组,正常对照组、尿促皮素0.1μmol.L-1组、星形孢菌素(Sta)1μmo.lL-1、H890.1μmol.L-1和维拉帕米(Ver)1μmol.L-1组及尿促皮素分别加Sta,H89和Ver组。采用体外培养的乳大鼠心肌细胞,应用尿促皮素0.1μmol.L-1诱导心肌肥大,观察Sta1μmol.L-1,H890.1μmo.lL-1和Ver1μmol.L-1的作用,进一步探讨尿促皮素0.1μmol.L-1诱导心肌肥厚的作用机制。用消化分离法及计算机图像分析系统检测心肌细胞直径;[3H]亮氨酸掺入法测定心肌细胞蛋白质的合成;用Lowry法检测心肌细胞蛋白质含量;用Western蛋白印迹法测定心房钠尿肽(ANP)表达;采用Till阳离子测定系统,以Fura-2/AM为荧光探针,观察心肌细胞[Ca2+]i瞬间变化。结果尿促皮素使心肌细胞直径、蛋白质合成、蛋白质含量和ANP表达分别增加30.9%,36.3%,35.5%和34.7%;尿促皮素+Sta组使心肌细胞直径、蛋白质合成、蛋白质含量和ANP表达分别降低了16.5%,22.1%,18.1%和21.3%;尿促皮素+H89组使心肌细胞直径、蛋白质合成、蛋白质含量和ANP表达分别降低了16.6%,21.5%,19.5%和20.6%;尿促皮素+Ver组使心肌细胞直径、蛋白质合成、蛋白质含量和ANP表达分别降低了17.1%,20.9%,17.9%及19.9%;尿促皮素能够使心肌细胞[Ca2+]i瞬间变化水平增高,Sta,H89和Ver能够降低尿促皮素引起的心肌细胞[Ca2+]i瞬间变化升高。结论尿促皮素可能通过蛋白激酶C和蛋白激酶A信号途径影响L-型Ca2+通道,进而影响细胞[Ca2+]i瞬间变化水平,诱导乳大鼠心肌细胞肥大。

Effect and mechanism of signal transduction pathway in urocortininduced cardiomyocytes hypertrophy in neonatal rat

AIM To investigate the effects and mechanism of cardiomyocyte hypertrophy induced by urocortin. METHODS The cardiomyocytes were divided into 8 groups: normal control, urocortin, staurosporine(Sta), verapamil(Ver), H89, urocortin+Sta, urocortin+Ver, and urocortin+H89 groups. The cardiomyocytes diameter was measured by computer photograph analysis system. The protein synthetic rate was obtained through measuring the incorporation of [~3H]-leucine into myocyte protein by liquid scintillation method. The total protein content was assayed by Lowry method. The expression of atrial natriuretic peptide (ANP) was determined by Western blot. [Ca~(2+)]_i transient was measured by Till image system by cell loading Fura-2/AM. RESULTSUrocortin group enhanced cardiomyocyte volume, protein synthesis, total protein content and expression of ANP by 30.9%, 36.3%, 35.5% and 34.7%;urocortin+Sta group decreased cardiomyocyte diameter, protein synthesis, total protein content and expression of ANP by 16.5%, 22.1%, 18.1% and 21.3%;urocortin+H89 group decreased the cardiomyocyte diameter, the protein synthesis,total protein content and expression of ANP by 16.6%, 21.5%, 19.5% and 20.6%;urocortin+Ver decreased the cardiomyocyte diameter, the protein synthesis, total protein content and the expression of ANP by 17.1%, 20.9%, 17.9% and 19.9%;Sta, H89 and Ver could decrease the [Ca~(2+)]_i transient induced by urocortin. CONCLUSION The hypertrophic effect of urocortin in rat neonatal cardiomyocytes is mediated via activation of protein kinase C and protein kinase A pathway and L-type calcium channels.