MORECULAR PHARMACOLOGICAL STUDY OF SIGNAL TRANSDUCTION

内皮素(ET)和血管紧张素II(Ang II)的激活所触发的信号转导过程在许多心血管疾病，即充血性心力衰竭中，在基因表达水平上对心肌细胞功能和疾病进展的病理生理调节起着至关重要的作用。α-肾上腺素受体的激活与这些受体所触发的信号转导相同。它们可能调节心肌肥大和重塑的过程。因此，研究这些受体激活后的信号转导对于了解心脏疾病的病理生理机制和制定治疗策略具有极其重要的意义。尽管二酰甘油诱导的蛋白激酶C的激活可能主要参与调节，但佛波酯可能激活蛋白激酶C和蛋白激酶C抑制剂，如Calphostin C和Chel…本研究旨在阐明信号转导途径，即PI水解酶在调节完整心肌细胞和心肌细胞收缩性能中的作用。ET-1和Ang II可引起细胞内Ca~(2+)动员增加，肌丝对Ca~(2+)的敏感性增加。推测PKC的激活和随后的Na~+/H~+交换器的激活导致细胞内碱化和细胞内Ca~(2+)~(2+)的继发性增加可能起着关键作用，但由于缺乏药物工具，在完整的心肌细胞中尚未获得令人信服的证据，具有足够高选择性的离子交换抑制剂。本研究阐明了选择性的Na~+/H~+交换器抑制剂HOE642和KB-R9032在不影响异丙肾上腺素对INDO-1负荷的兔单个心肌细胞的正性肌力作用(缩短增加)的作用。而Na~+/Ca~(2+)&gt；阻断剂KB-R7943可抑制ET-1引起的钙瞬变增加。全细胞膜片钳实验表明，ET-1对兔心肌细胞L型钙电流无明显影响。Ang II也得到了类似的结果。这些结果表明，ET-1和Ang II通过激活受体激活离子交换器，在调节完整心肌细胞的Ca~(2+)&Gt~(2+)信号中起关键作用。较少

Signal transduction processes triggered by activation of endothelin (ET) and angiotensin II (Ang II) play a crucial role in a number of cardiovascular diseases, namely in congestive heart failure, for the pathophysiological regulation of myocardial cell function and progression of the disease at the level of gene expression. Activation of α-adrenoceptors shares signal transduction triggered by these receptors. They may regulate the process of cardiac hypertrophy and remodeling. Therefore the study on the signal transduction subsequent to activation of these classes of receptor is of extreme importance for understanding of pathophysiology of cardiac diseases and for constitution of therapeutic strategies. Although activation of protein kinase C (PKC) induced by diacylglycerol (DAG), the product of stimulation of PI hydrolysis resulting from receptor activation, may be primarily involved in the regulation, phorbol esters that activate PKC and PKC inhibitors, such as calphostin C and chel … More erythrine, do not mimic the regulatory effect of receptor stimulation in intact myocardial cells.The study was carried out to elucidate the role of signal transduction, namely PI hydrolysis, in regulation of myocardial contractility in intact myocardium and myocytes. ET-1 and Ang II elicit an increase in intracellular Ca^<2+> mobilization and an increase in myofilament Ca^<2+> sensitivity. It has been postulated that the activation of PKC and subsequent activation of Na^+/H^+ exchanger that leads to intracellular alkalinization and secondary increase in intracellular Ca^<2+> ions may play a crucial role, but compelling pieces of evidence have not yet been obtained because of lack of pharmacological tools, ion exchange inhibitors, with sufficiently high selectivity, in intact myocardium.In the present study, it was clarified that selective inhibitors of Na^+/H^+ exchanger HOE642 and KB-R9032 inhibited the positive inotropic effect (the increase in shortening) of ET-1 without affecting the effect of isoproterenol in rabbit single myocytes loaded with indo-1. On the other hand, the increase in Ca^<2+> transients induced by ET-1 was inhibited by the Na^+/Ca^<2+> inhibitor KB-R7943. It became evident that ET-1 did not cause a prominent effect on L-type Ca^<2+> current by means of whole cell patch clamp in rabbit myocytes. Similar results have been obtained also with Ang II. These results indicate that stimulation of ion exchangers mediated by receptor activation with ET-1 and Ang II plays a crucial role in regulation of Ca^<2+> signaling in intact myocardial cells. Less