Premium
Regulation of Cyclic AMP Levels by Calcium in Bovine Adrenal Medullary Cells
Author(s) -
Keogh Rosemary,
Marley Philip D.
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.tb06373.x
Subject(s) - veratridine , endocrinology , medicine , extracellular , depolarization , calcium , adrenal medulla , tetrodotoxin , cyclase , histamine , adenylate kinase , chemistry , chromaffin cell , catecholamine , hexamethonium , ionophore , biophysics , acetylcholine , biology , biochemistry , stimulation , sodium , receptor , organic chemistry , sodium channel
: Both nicotine and histamine have been reported to increase cyclic AMP levels in chromaffin cells by Ca 2+ ‐dependent mechanisms. The present study investigated whether Ca 2+ was an adequate and sufficient signal for increasing cyclic AMP in cultured bovine adrenal medullary cells. Depolarization with 50 m M K + caused a two‐to threefold increase in cellular cyclic AMP levels over 5 min, with no change in extracellular cyclic AMP. This response was abolished by omission of extracellular Ca 2+ and by 100 μ M methoxyverapamil, and was unaffected by 1 μ M tetrodotoxin and by 1 m M isobutylmethylxanthine. Veratridine (40 μ M ) also increased cellular cyclic AMP levels by two‐to fourfold. This response was abolished by either methoxyverapamil or tetrodotoxin. The Ca 2+ ionophore A23187 (10–50 μ M ) had little or no effect on cellular cyclic AMP levels. When the concentration of K + used to depolarize the cells was reduced to 12–15 m M , the catecholamine release was similar to that induced by 50 μ M A23187, and the cyclic AMP response was almost abolished. The results suggest that Ca 2+ entry into chromaffin cells is a sufficient stimulus for increasing cellular cyclic AMP production. The possible involvement of a Ca 2+ /calmodulin‐dependent isozyme of adenylate cyclase is discussed.