EVIDENCE AGAINST THE ASSOCIATION OF THE SULFONYLUREA RECEPTOR WITH ENDOGENOUS KIR FAMILY MEMBERS OTHER THAN K-ATP IN CORONARY VASCULAR SMOOTH-MUSCLE

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