EDHFとGap Junction
詳細
Connexins are expressed in vascular endothelial and smooth muscle cells. However, the roles of connexins in the regulation of arterial tone are unclear. In this symposium, we would like to introduce recent evidence that connexins mediate endothelium dependent arterial relaxation caused by endothelium-derived hyperpolarizing factor (EDHF). The molecular identity of EDHF is not convincing. We assessed that whether NO, PGI2, K+, anandamide, H2O2 or EET act as EDHF. However, none of that act as EDHF in rat mesenteric artery. Recent studies suggest that gap junctional communication between endothelium and smooth muscle may account for EDHF responses. In rat mesenteric artery, endothelium-dependent relaxation and hyperpolarization by EDHF were inhibited by gap junction inhibitors. RT-PCR experiment showed that connexin 37, 40, 43 & 45 were expressed in the artery. In immunohistochemistory, connexin37, 40 & 43 were expressed in endothelium and connexin 43 was expressed in smooth muscle cells. EDHF-mediate hyperpolarization and relaxation were correlated with serum estrogen level. The expressional levels of connexin40 & 43 were also dependent on estrogen level. These results suggest that EDHF is not a molecule and its responses are mediated by gap junctional communications. Connexin may play a pivotal role in the regulation arterial tone in physiological and pathophysiological states in especially small arteries. [J Physiol Sci. 2006;56 Suppl:S29]
