Modulation of K(ATP) currents in rat ventricular myocytes by hypoxia and a redox reaction.
OBJECTIVE
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)/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 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 Ca2+/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.


CONCLUSIONS
The present study provides electrophysiological evidence that hypoxia and the oxidizing reaction are closely related to the modulation of I(KATP).
Cardio-Electrophysiological Research Laboratory, Medical College, Wuhan University of Science and Technology, Wuhan 430065, China.
Xi-Sheng
XS
Yan
Ji-Hua
JH
Ma
Pei-Hua
PH
Zhang
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001596:Benzylamines / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002227:Carbazoles / Q000494:pharmacology; D002478:Cells, Cultured; D017869:Cyclic GMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D005978:Glutathione / Q000494:pharmacology; D019803:Glutathione Disulfide / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D000860:Hypoxia / Q000378:metabolism*; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D013449:Sulfonamides / Q000494:pharmacology; D013997:Time Factors; D000096926:Benzenesulfonamides
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D001596:Benzylamines; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002227:Carbazoles; D017869:Cyclic GMP-Dependent Protein Kinases; D004229:Dithiothreitol; D005978:Glutathione; D019803:Glutathione Disulfide; D006861:Hydrogen Peroxide; D007211:Indoles; D008301:Maleimides; D024661:Potassium Channels, Inwardly Rectifying; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; C073601:KT 5823; C072105:KN 93; D000096926:Benzenesulfonamides; C063302:KN 62; C088060:bisindolylmaleimide