Rapid endocitosis in mouse chromaffin cells is controlled by intracellular and extracellular calcium sources

A. VERONICA BELINGHERI; F.D. MARENGO

Huerta Grande. Córdoba.

Congreso; II Reunión Conjunta de Neurociencias; 2010

Sociedad Argentina de Neurociencias y Taller Argentino de Neurociencias

Endocytosis is critical for maintaining membrane homeostasis and secretion reliability in neuroendocrine cells. Chromaffin cell rapid endocytosis (RE) is a Ca2+ dependent process that overcomes previous exocytosis at a Ca2+ entry more than 75pC, i.e. excess retrieval (EX). In order to study the Ca2+ sources that regulate RE we used patch clamp capacitance measurements, and applied specific pharmacological agents. We found that the L-Ca2+ channel blocker nitrendipine (10µM) completely inhibited RE. As in many cells Ca2+ entry through L-Ca2+ channels is coupled to Ca2+ release from endoplasmic reticulum, we tested the effect of Ryanodine (Ry) on RE. Ry (100µM) partially inhibited RE (by 62%) and completely blocked excess retrieval. To identify if RE is activated by a global or local Ca2+ signal, we replaced EGTA in the internal solution by the fast Ca2+ buffer BAPTA. A partial inhibition of RE (by 25%) and a reduction of EX (by 66%) was observed. We conclude that RE is triggered by a localized Ca2+ increase provoked by a combined action of Ca2+ entry through L-Ca2+ channels and Ca2+ release from endoplasmic reticulum.