Colocalization of glycolytic enzyme activity and K-ATP channels in basolateral membrane of Necturus enterocytes

Rb-86 fluxes through ATP-regulated K+ (K-ATP) channels in membrane vesicles derived from basolateral membranes of Necturus small intestinal epithelial cells as well as the activity of single K-ATP channels reconstituted into planar phospholipid bilayers are inhibited by the presence of ADP plus phos phoenolpyruvate in the solution bathing the inner surface of these channels . This inhibition can be prevented by pretreatment of the membranes with 2, 3-butanedione, an irreversible inhibitor of pyruvate kinase (PK) and revers ed by the addition of 2-deoxyglucose plus hexokinase. The results of additi onal studies indicate that PK activity appears to be tightly associated wit h this membrane fraction. These results, together with considerations of th e possible ratio of Na+-K+ pumps to K-ATP channels in the basolateral membr ane, raise the possibility that "cross talk" between those channels and pum ps (i.e., the "pump-leak parallelism") may be mediated by local, functional ly compartmentalized ATP-to-ADP ratios that differ from those in the bulk c ytoplasm.