Cinemicrographic studies on beta granule movement in monolayer culture of islet cells.

Monolayer cultures of adult rat islets were used for cinemicrographic studies on the movement of beta granules in the cytoplasm of beta cells. Stimulation of insulin release by glucose produced a significant increase in the amount of beta granule movement in the cultured cells. Disruption of the microtubular system with vinblastine or stabilization of microtubules with deuterium oxide inhibited the induction of granule movement by glucose. Incubation of the cultures in the absence of calcium inhibited glucose-induced movement of beta granules, whereas the subsequent addition of calcium permitted movement to occur. The addition of epinephrine also inhibited glucose-induced beta granule movement. In the presence of nonstimulating levels of glucose, movement of beta granules was present. The amount of movement varied from cell to cell suggesting a difference in base line activity of individual beta cells. The movement of individual beta granules was saltatory in type, and the average rate of movement was 1.5 mum. per second. The study demonstrated that directed movement of beta granules occurs following stimulation with glucose and adds further support to the hypothesis that the microtubular-microfilamentous system is involved in the intracellular translocation of beta granules to the cell surface where they are released by emiocytosis.