Modulation of K ATP currents in rat ventricular myocytes by hypoxia and a redox reaction

Aim: The present study investigated the possible regulatory mechanisms of redox agents and hypoxia on the K ATP current ( I KATP ) in acutely isolated rat ventricular myocytes. Methods: Single-channel and whole-cell patch-clamp techniques were used to record the K ATP current ( I KATP ) in acutely isolated rat ventricular myocytes. Results: Oxidized glutathione (GSSG, 1 mmol/L) increased the I KATP , while reduced glutathione (GSH, 1 mmol/L) could reverse the increased I KATP during normoxia. To further corroborate the effect of the redox agent on the K ATP channel, we employed the redox couple DTT (1 mmol/L)/H 2 O 2 (0.3, 0.6, and 1 mmol/L) and repeated the previous processes, which produced results similar to the previous redox couple GSH/GSSG during normoxia. H 2 O 2 increased the I KATP in a concentration dependent manner, which was reversed by DTT (1 mmol/L). In addition, our results have shown that 15 min of hypoxia increased the I KATP , while GSH (1 mmol/L) could reverse the increased I KATP . Furthermore, in order to study the signaling pathways of the I KATP augmented by hypoxia and the redox agent, we applied a protein kinase C(PKC) inhibitor bisindolylmaleimide VI (BIM), a protein kinase G(PKG) inhibitor KT5823, a protein kinase A (PKA) inhibitor H-89, and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitors KN-62 and KN-93. The results indicated that BIM, KT5823, KN-62, and KN-93, but not H-89, inhibited the I KATP augmented by hypoxia and GSSG; in addition, these results suggest that the effects of both GSSG and hypoxia on K ATP channels involve the activation of the PKC, PKG, and CaMK II pathways, but not the PKA pathway. Conclusion: The present study provides electrophysiological evidence that hypoxia and the oxidizing reaction are closely related to the modulation of I KATP .