Evidence against the association of the sulphonylurea receptor with endogenous Kir family members other than KATP in coronary vascular smooth muscle.

We used whole-cell patch clamp to record inward rectifier (KIR) and ATP-sensitive (KATP) K+ currents from pig coronary arterial myocytes. KIR currents were blocked by Ba2+ ions with a KD around 3 microM, but were unaffected by 10 microM glibenclamide, and only reduced 16% by 100 microM of the sulphonlyurea (n=4). In contrast, pinacidil-activated KATP currents were over 1000 times more sensitive to glibenclamide, being inhibited with a KD close to 100 nM (n=5). Our findings suggest that the sulphonylurea receptor (SUR) in these cells associates with the appropriate subunits of the Kir family to form KATP channels, but does not show promiscuous association with subunits that form the strong inward rectifier KIR.