The inhibitory effect of exogenous nitric oxide (NO) on the open state of ATP-sensitive potassium channels (KATP) and its underlying mechanism remain unclear. In this study, patch-clamp and molecular biology techniques are used to investigate this issue. In acutely isolated rat mesenteric artery smooth muscle cells and human embryonic kidney 293 cells (HEK293) expressing inwardly rectifying potassium channel 6.1 subunit/sulfonylurea receptor 2B subunit (Kir6.1/SUR2B), sodium nitroprusside (SNP) was found to significantly inhibit the activity of open KATP channels. Detection using biotin-labeled glutathione ethyl ester (BioGEE) combined with Western blotting showed that Kir6.1 subunit glutathionylation level was significantly decreased after SNP treatment. These results indicate that exogenous NO directly inhibits the activity of open KATP channels by nitrosylating key cysteine residues of the Kir6.1 subunit and competitively inhibiting glutathionylation at this site. This study provides new experimental evidence for the molecular mechanism of NO in vascular regulation.
