Rapid vesicle replenishment after the immediately releasable pool exocytosis is tightly linked to fast endocytosis, and depends on basal calcium and cortical actin in chromaffin cells

The maintenance of the secretory response requires a continuous replenishment releasable vesicles. It was proposed that immediately pool (IRP) is important in chromaffin cell secretion during action potentials applied at basal physiological frequencies, because proximity IRP vesicles to voltage dependent Ca2+ channels. However, previous reports showed after depletion too slow manage such situation. In this work we used patch-clamp measurements membrane capacitance, confocal imaging F-actin distribution and cytosolic with Fura-2 re-analyze problem primary cultures mouse cells. We provide evidence has one (time constant between 5-10 s) rapid component 0.5-1.5 linked dynamin-dependent fast endocytosis. Both, endocytosis were eliminated when 500 nM added internal solution experiments, but they became dominant accelerated buffer capacity increased. addition, both retarded cortical cytoskeleton disrupted cytochalasin D. Finally, permeabilized cells stained rhodamine-phalloidin, density reduced concentration increased range 10-1000 nM. conclude low concentrations, which favor stabilization, allow activation mechanism IRP.