Disruption of the actin cytoskeleton abolishes high affinity 3H-glibenclamide binding in rat aortic rings

Abstract

The interaction between the cytoskeleton and the ATP-sensitive K⁺ channel (K_ATP channel) was studied in rat aortic rings by examining the binding of the sulphonylurea blocker, ³H-glibenclamide, and of the opener, ³H-P1075.

The actin cytoskeleton disrupting agents, cytochalasin D (1μM) and latrunculin B (1μM), abolished the high affinity component of ³H-glibenclamide binding. Preincubation with the actin cytoskeleton stabilizing agent, phalloidin (10μM) prevented the effect of cytochalasin D. In contrast, binding of the opener, ³H-P1075, and inhibition of this binding by glibenclamide, were unaffected by cytochalasin D (3μM). Colchicine (100μM), which disassembles microtubules, had no effect on the binding of ³H-glibenclamide and ³H-P1075.

The data show that high affinity binding of glibenclamide, which mediates the effects of the sulphonylurea in this preparation, requires the presence of an intact actin cytoskeleton. Binding of the opener is unaffected by the state of the cytoskeleton and preserves a conformational state in which high affinity binding of glibenclamide to the sulphonylurea receptor can occur.