Highly coupled exocytosis in chromaffin cells

FERNANDO D. MARENGO

Buenos Aires

Congreso; Congreso de la Sociedad Argentina de Fisiología 2014; 2014

Sociedad Argentina de Fisiología

conclusions IRP is a pool of approximately 20 ready releasable vesicles closely coupled to Ca2+ current activation. Our results indicate that there is a high functional coupling between IRP vesicles and P/Q-type Ca2+ channels. This coupling can be explained by the interaction between the synprint region of the α1A subunit and vesicles. This coupling increases markedly the efficiency of Ca2+ current to trigger exocytosis. The refilling of IRP after depletion is too slow ( = 7.5 s) to expect a significant contribution of this pool to exocytosis during repetitive stimulation at physiological frequencies. The application of a depolarization pulse that approximate the shape, duration and amplitude of chromaffin cell action potential induces the exocytosis of a small group of vesicles that recovers rapidly with a  = 0.73 s. This fast rate of recovery can account for sustained exocytosis at low frequencies in the physiological range. This fast recovery can be explained by a combined contribution of vesicles provided by upstream vesicle pools and local recycling.