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First published online July 6, 2005
Journal of Experimental Biology 208, 2765-2772 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01704

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Cardioprotective effects of K_ATP channel activation during hypoxia in goldfish Carassius auratus

Jerri Chen, Julia X. Zhu, Ingred Wilson and John S. Cameron^*

Department of Biological Sciences, Wellesley College, Wellesley, MA 02481, USA

^* Author for correspondence (e-mail: jcameron{at}wellesley.edu)

Accepted 19 May 2005

The activation of ATP-sensitive potassium (K_ATP) ion channels in the heart is thought to exert a cardioprotective effect under low oxygen conditions, possibly enhancing tolerance of environmental hypoxia in aquatic vertebrates. The purpose of this study was to examine the possibility that hypoxia-induced activation of cardiac K_ATP channels, whether in the sarcolemma (sarcK_ATP) or mitochondria (mitoK_ATP), enhances viability in cardiac muscle cells from a species highly tolerant of low oxygen environments, the goldfish Carassius auratus. During moderate hypoxia (6–7 kPa), the activation of sarcK_ATP channels was indicated by a reduction in transmembrane action potential duration (APD). This response to hypoxia was mimicked by the NO-donor SNAP (100 µmol l^–1) and the stable cGMP analog 8-Br-cGMP, but abolished by glibenclamide or L-NAME, an inhibitor of NO synthesis. The mitoK_ATP channel opener diazoxide did not affect APD. Isolated ventricular muscle cells were then incubated under normoxic and hypoxic conditions. Cell viability was decreased in hypoxia; however, the negative effects of low oxygen were reduced during simultaneous exposure to SNAP, 8-Br-cGMP, and diazoxide. The cardioprotective effect of diazoxide, but not 8-Br-cGMP, was reduced by the mitoK_ATP channel blocker 5-HD. These data suggest that hypoxia-induced activation of sarcK_ATP or mitoK_ATP channels could enhance tolerance of low-oxygen environments in this species, and that sarcK_ATP activity is increased through a NO and cGMP-dependent pathway.

Key words: hypoxia, ATP-sensitive K⁺ channels, K_ATP, nitric oxide, cardioprotection, goldfish, Carassius auratus

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