Na+ - K+ pump 억제가 토끼 도관동맥과 저항동맥의 수축과 이완에 미치는 영향

Objectives: Recently endogenous digitalits-like substances were found in the blood of various cardiovascular diseases and they have been considered as one of the causes developing hypertension. Whereas the pathophysiology of the hypertension developed by endogeous digitalis-like substances has not been clarified yet. The purpose of this study is to investigate the effects of Na+-K+ pump blocking on the contractility of blood vessel(conduit and resistant artery) of rabbit. Methods: We used the rings of abdominal aorta and branches of sup. mesenteric artery of rabbits as conduit arteries and resistant arteries respectively. Na+-K+ pump blocking was obtained by treatment with [K+]o solution or ouabain 10μM solution for 30 minutes. The vascular responses to vasoconstrictors or vasodilators were measured by organ bath study and cyclic GMP measurement. Results: Basal tension was elevated by blocking of Na+-K+ pump with [K+]o solution. The increase of basal tension in the aortic rings without endothelium was significantly greater than that in the rings with endothelium. The magnitudes of contractions of aortic rings by norepinephrine, serotonin and acetylcholine were significantly increased by the blocking of Na+-K+ pump. The magnitudes of endothelium-dependent relaxation and relaxation induced by sodium nitroprusside and isoproterenol in aortic rings were decreased by the blocking of Na+-K+ pump. The endothelium-dependent increase of cyclic GMP level in smooth muscle was attenuated by the blocking of Na+-K+ pump. In branches of sup. mesenteric arteries, the increase of norepinephrine induced contraction by ouabain was greater than that of in aortic rings and endothelium-dependent relaxation was completely blocked by the treatment with ouabain. Conclusion: It could be suggested that the contractility of vascular smooth muscle with the blocking of Na+-K+ pump was increased and the responsivenesses of vascular smooth muscle to vasorelaxing agents were decreased. These findings suggest that endogenous digitalis-like substances may play an important role in pathogenesis of essential hypertension. Also these findings make an offer how to develop the functional changes in smooth muscle and ednothelium of blood vessels in hypertension.