Portal de Periódicos da CAPES

5′‐( N ‐Ethylcarboxamido)adenosine Inhibits Ca 2+ Influx and Activates a Protein Phosphatase in Bovine Adrenal Chromaffin Cells

1995; Wiley; Volume: 64; Issue: 1 Linguagem: Inglês

10.1046/j.1471-4159.1995.64010077.x

1471-4159

Jesús Mateo, Enrique Castro, Jean Zwiller, Dominique Aunis, Marı́a Teresa Miras-Portugal,

Endoplasmic Reticulum Stress and Disease

Abstract: We investigated the effect of the adenosine receptor agonist 5′‐( N ‐ethylcarboxamido)adenosine (NECA) in catecholamine secretion from adrenal chromaffin cells that exhibit only the A 2b subtype adenosine receptor. NECA reduced catecholamine release evoked by the nicotinic agonist 1,1‐dimethyl‐4‐phenylpiperazinium (DMPP) in a time‐dependent manner. Inhibition reached 25% after 30–40‐min exposure to NECA. This effect on DMPP‐evoked catecholamine secretion was mirrored by a similar (27.7 ± 3.3%), slowly developing inhibition of [Ca 2+ ] i transients induced by DMPP that peaked at 30‐min preincubation with NECA. The capacity of the chromaffin cells to buffer Ca 2+ load was not affected by the treatment with NECA. Short‐term treatment with NECA failed both to modify [Ca 2+ ] i levels and to increase endogenous diacylglycerol production, showing that NECA does not activate the intracellular Ca 2+ /protein kinase C signaling pathway. The inhibitory effects of NECA were accompanied by a 30% increase of protein phosphatase activity in chromaffin cell cytosol. We suggest that dephosphorylation of a protein involved in DMPP‐evoked Ca 2+ influx pathway (e.g., L‐type Ca 2+ channels) could be the mechanism of the inhibitory action of adenosine receptor stimulation on catecholamine secretion from adrenal chromaffin cells.