A study forthe effects of estrogen on actions ofendothelium-derived hyperpolarizing factor

内皮源性超极化因子（Endothelium-derived hyperpolarizing factor，EDHF）是由内皮细胞释放的一种具有开放血管、调节血压和器官微循环等功能的因子，目前认为EDHF的候选者有P450代谢产物、H_2O_2和钾离子等，其中一种是通过缝隙连接介导内皮细胞膜超极化的电传递。雌激素是心脏和血管保护，有助于帮助妇女免受动脉粥样硬化和缺血性心脏病。保护性行动可能部分源于其对EDHF的影响。由于缝隙连接由连接蛋白组成，并且它们受雌激素的显著调节，我们试图以雌激素为线索来研究EDHF的本质。对中年雌性大鼠行卵巢切除（OVX）或雌激素替代（ERT），并与假手术组（CON）进行比较。内皮完整的肠系膜动脉静息膜电位OVX组较CON组浅，ERT组则相反。乙酰胆碱诱导的肠系膜动脉超极化和舒张在OVX中受损，在ERT中恢复。用特异性抗体免疫组化显示，与CON和ERT相比，OVX组连接蛋白43的表达明显减少。Western blotting结果显示，与其他各组相比，去卵巢组的Cx43蛋白表达量明显降低。为了进一步研究EDHF的性质，我们检查了K通道mRNA的存在，现在开始寻找这些通道在EDHF功能中的作用。

Endothelium-derived hyperpolarizing factor (EDHF) is released from endothelial cells and function to open reseitance vessels and have a pivotal role in the regulation of blood pressure and microcirculalion of organs.There are some candidates for EDHF, such as P450 metabolite, H_2O_2 and pottasium ion, and one of EDHFs is now thought to be electrical transmission of hypeipolarization of the endothelial cell membrane through gap junction. Estrogen is cardio- and vessel-protective and contributes to help women free from atherosclerosis and ischemic heart disease. The protective actions may arise, in part, from its effect on EDHF. Since gap junction consists of connexins and they are dramatically modulated by estrogen, we tried to investigate the nature of EDHF using estrogen as a clue. Middle-aged female rats was ovariectomized (OVX) or then estrogen-replaced (ERT), and compared with sham-operated ones (CON). The resting membrane potential of the endothelium-intact mesenteric artery of OVX was shallower than that of CON, and reversed in ERT. Acetylcholine-induced hypeipolarization and relaxation of the mesenteric artery were impaired in OVX and recovered in ERT. Immunostaining of connexin 43 using specific antibody revealed a confound decrease in connexin in OVX compared with CON and ERT. Western blotting of connexin 43 protein showed a decrease in the protein expression in OVX compared with the others. To further investigate the nature of EDHF we checked the presence of mRNAs of K channels and now started seeking the role of these channels in EDHF function.