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ENDOTHELIN AND ATP-SENSITIVE POTASSIUM CHANNEL MEDIATE ELECTROPHYSIOLOGICAL CHANGES INDUC BY HYPOXIA IN RABBIT SINOATRIAL NODEED

ZHANG ZHAO, SUN GUANG-QI, LI YU-LONG, HE RUI-RONG

Department of Physiology, Institute of Basic Medicine, Hebei Medical Unvwsity, Shijiax} 050017)

Abstract

The role of ET and K_(ATP) channel in hypoxia-induced negative chronotropic effect of pacemaker cells in rabbit sinoatrial node was studied with intracellular microelectrode technique. The results obtained were as follows:(1)Hypoxia produced a progressive decrease in the velocity of diastolic depolarization (VDD) of pacemaker cells resulting in a reduced rate of pacemaker firing (RPF)，and induced a decrease in APD，especially
APD5o. (2) K_(ATP) channel opener cromakalim markedly induced a negative chronotropic effect in a concentration-dependent manner and significantly shortened APD5o. K_(ATP )channel blocker glibenclamide alleviated.the effects of hypoxia on pacemaker cells，thereby suggesting the involvement of KATP channel in the hypoxia-induced effects.(3) By superfusion of ET-1，the hypoxia-induced decrease in RPF was remarkably potentiated and the occurrence of pacemaker arrest was shifted to an earlier time. The h3,poxia-induced effects could be effectively attenuated after pretreatment with BQ-123，implying the role of endogenous ET-1 release in hypoxia-induced effects. It is conclud
ed that the negative chronotropic effect and the decrease in APD induced by hypoxia may be attributed to the activation of K_(ATP)channel and the release of endogenous ET.

Key words: Hypoxia; sinoatrial node;KprP channel;Endothelin; cromakalim;glibenclamide; BQ123;electrophysiology

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Citing This Article：

ZHANG ZHAO, SUN GUANG-QI, LI YU-LONG, HE RUI-RONG. ENDOTHELIN AND ATP-SENSITIVE POTASSIUM CHANNEL MEDIATE ELECTROPHYSIOLOGICAL CHANGES INDUC BY HYPOXIA IN RABBIT SINOATRIAL NODEED . Acta Physiol Sin 1996; 48 (3): (in Chinese with English abstract).