Dynamics of insulin release and microtubular-microfilamentous system. I. Effect of cytochalasin B

In order to assess the participation of the microfilamentous cell web in the multiphasic response of the pancreatic beta cell, the effect of cytochalasin B upon both glucose- and sulfonylurea-induced insulin release was investigated in the perfused isolated pancreas. Cytochalasin B failed to affect the basal rate of insulin release, but enhanced the initial and later phases of insulin secretion in response to either glucose or gliclazide. In addition, cytochalasin B lowered the threshold concentration for the stimulant action of glucose upon insulin release. Ultrastructural studies supported the concept of a specific interaction of cytochalasin B with the microfilamentous cell web of the beta cell. It is concluded that the integrity of such a structure is equally important for both the initial and later secretory responses of the beta cell to various insulinotropic agents.