Modulation of KATP currents in rat ventricular myocytes by hypoxia and a redox reaction
Abstract
Aim: The present study investigated the possible regulatory mechanisms of redox agents and hypoxia on the KATP current (IKATP) in acutely isolated rat ventricular myocytes.
Methods: Single-channel and whole-cell patch-clamp techniques were used to record the KATP current (IKATP) in acutely isolated rat ventricular myocytes.
Results: Oxidized glutathione (GSSG, 1 mmol/L) increased the IKATP, while reduced glutathione (GSH, 1 mmol/L) could reverse the increased IKATP during normoxia. To further corroborate the effect of the redox agent on the KATP channel, we employed the redox couple DTT (1 mmol/L)/H2O2 (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. H2O2 increased the IKATP 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 IKATP, while GSH (1 mmol/L) could reverse the increased IKATP. Furthermore, in order to study the signaling pathways of the IKATP 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 IKATP augmented by hypoxia and GSSG; in addition, these results suggest that the effects of both GSSG and hypoxia on KATP 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 IKATP.
Keywords:
Methods: Single-channel and whole-cell patch-clamp techniques were used to record the KATP current (IKATP) in acutely isolated rat ventricular myocytes.
Results: Oxidized glutathione (GSSG, 1 mmol/L) increased the IKATP, while reduced glutathione (GSH, 1 mmol/L) could reverse the increased IKATP during normoxia. To further corroborate the effect of the redox agent on the KATP channel, we employed the redox couple DTT (1 mmol/L)/H2O2 (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. H2O2 increased the IKATP 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 IKATP, while GSH (1 mmol/L) could reverse the increased IKATP. Furthermore, in order to study the signaling pathways of the IKATP 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 IKATP augmented by hypoxia and GSSG; in addition, these results suggest that the effects of both GSSG and hypoxia on KATP 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 IKATP.