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Prostaglandin E 2 Activates Ca 2+ Channels in Bovine Adrenal Chromaffin Cells
Author(s) -
MochizukiOda Noriko,
Mori Kensaku,
Negishi Manabu,
Ito Seiji
Publication year - 1991
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1991.tb08183.x
Subject(s) - extracellular , depolarization , chromaffin cell , biophysics , chemistry , patch clamp , membrane potential , intracellular , endocrinology , reversal potential , medicine , prostaglandin e , voltage clamp , current clamp , channel blocker , inositol , electrophysiology , fura 2 , inositol trisphosphate , calcium , biology , adrenal medulla , biochemistry , catecholamine , receptor , cytosol , enzyme
We have demonstrated that prostaglandin E 2 (PGE 2 ) treatment of bovine adrenal chromaffin cells results in a sustained elevation of intracellular Ca 2+ concentration ([Ca 2+ ] i ) in these cells. Because the continued elevation of [Ca 2+ ] i was dependent on extracellular Ca 2+ concentration, it can be assumed that the PGE 2 ‐induced [Ca 2+ ] i increase is due, at least in part, to an opening of membrane Ca 2+ channels. In this study, we used electrophysiological methods to examine the mechanism of the PGE 2 ‐induced [Ca 2+ ] i increase directly. Puff application of PGE 2 to the external medium resulted in a prolonged depolarization in about half of the chromaffin cells examined. In whole‐cell voltage‐clamp recordings, an increase in inward current was observed over a 6–7‐min period following bath application of PGE 2 (± 10 μ M ), even in the absence of external Na + . This inward current was abolished when the recordings were made with the cells in a Ca 2+ ‐free medium, but it was not inhibited by Mn 2+ , a blocker of voltage‐dependent Ca 2+ channels. In cell‐attached patch‐clamp configuration, PGE 2 produced an increase in the opening frequency of inward currents. The reversal potential of the PGE 2 ‐induced currents was about +40 mV, which is close to the reversal potential of the Ca 2+ channel. The opening frequency was not affected by membrane potential changes. In inside‐out patch‐clamp configuration, inositol 1,4,5‐trisphosphate (2 μ M ) added to the cytoplasmic side activated the Ca 2+ ‐channel currents, but PGE 2 was ineffective when applied to the cytoplasmic side. These results suggest that PGE 2 activates voltage‐independent Ca 2+ channels in chromaffin cells through a diffusible second messenger, possibly inositol 1,4,5‐trisphosphate.