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Internal Ca 2+ Mobilization by Muscarinic Stimulation Increases Secretion from Adrenal Chromaffin Cells Only in the Presence of Ca 2+ Influx
Author(s) -
Yamagami Kazuhiko,
Nishimura Shigeto,
Sorimachi Masaru
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.tb06368.x
Subject(s) - muscarinic acetylcholine receptor , secretion , endocrinology , medicine , intracellular , stimulation , chromaffin cell , fura 2 , chemistry , muscarinic agonist , catecholamine , extracellular , adrenal medulla , cytosol , biology , receptor , carbachol , biochemistry , enzyme
: The cytosolic free Ca 2+ concentration ([Ca 2+ ] m ) in single cat and bovine adrenal chromaffin cells was measured to determine whether or not there was any correlation between the [Ca 2+ ] m and the catecholamine (CA) secretion caused by muscarinic receptor stimulation. In cat chromaffin cells, methacholine (MCh), a muscarinic agonist, raised [Ca 2+ ] m by activating both Ca 2+ influx and intracellular Ca 2+ mobilization with an accompanying CA secretion. In bovine cells, MCh elevated [Ca 2+ ] m by mobilizing intracellular Ca 2+ but did not cause CA secretion. The MCh‐induced rise in [Ca 2+ ] m in cat cells was much higher than that in bovine cells, but when Ca 2+ influx was blocked, the rise was reduced, with a concomitant loss of secretion, to a level comparable to that in bovine cells. Intracellular Ca 2+ mobilization due to muscarinic stimulation substantially increased secretion from depolarized bovine and cat cells, where a [Ca 2+ ] m elevated above basal values was maintained by a continuous Ca 2+ influx. These results show that Ca 2+ released from internal stores is not effective in triggering secretion unless Ca 2+ continues to enter across the plasma membrane, a conclusion suggesting that secretion depends on [Ca 2+ ] m in a particular region of the cell.