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Possible Regulation of Caffeine‐Induced Intracellular Ca 2+ Mobilization by Intracellular Free Na +
Author(s) -
Sorimachi Masaru,
Yamagami Kazuhiko,
Nishimura Shigeto,
Kuramoto Kuniaki
Publication year - 1992
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.1471-4159.1992.tb10120.x
Subject(s) - intracellular , caffeine , mobilization , chemistry , biophysics , microbiology and biotechnology , biochemistry , biology , endocrinology , political science , law
Abstract: To gain some understanding of the regulatory mechanism involved in caffeine‐induced Ca 2+ release in adrenal chromaffin cells, we took advantage of the paradoxical observation that removal of divalent cations potentiated the secretory response to caffeine. We measured the concentration of cytosolic free Ca 2+ ([Ca] in ) in isolated cat chromaffin cells, by fura‐2 microfluorometry, to see whether there was any correlation between the secretory response and the rise in [Ca] in . The caffeine‐induced [Ca] in rise and catecholamine secretion were increased by treatment of cells with a divalent cation‐deficient solution. These potentiated responses were strongly inhibited either by pretreatment with ryanodine, by the reduction of the external Na + concentration, or by the addition of Ca 2+ channel blockers. Removal of divalent cations caused a large rise in the cytosolic free Na + concentration ([Na] in ), which was measured using SBFI microfluorometry. This rise in [Na] in was reduced either by adding Ca 2+ channel blockers or by reducing the external Na + concentration. These results show a good correlation between caffeine‐induced Ca 2+ release and [Na] in at the time of stimulation, suggesting that caffeine‐induced Ca 2+ release is regulated by [Na] in .