期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1978
卷号：75
期号：5
页码：2234-2238
DOI：10.1073/pnas.75.5.2234
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Isolated rat hepatocytes do not actively accumulate Ca2+ during prolonged incubation in vitro; however, these cells do exhibit a limited exchange of intracellular with extracellular Ca2+. The exchangeable pool represents about 2 nmol of Ca2+ per mg of protein. In medium containing either a low (20 {micro}M) or high (1 mM) concentration of Ca2+, the divalent cation ionophore, A23187 (at concentrations of 0.03-0.1 nmol/mg of protein), causes release of 45Ca2+ from this exchangeable pool but does not allow net influx of extracellular Ca2+ detectable by the use of a Ca2+-sensitive electrode. Like A23187, the hormones norepinephrine, vasopressin, and glucagon (at concentrations that stimulate gluconeogenesis) each induces a similar net efflux of Ca2+. Treatment with one hormone decreases the subsequent reponse to the others, whereas treatment with A23187 abolishes the hormonal effects upon both Ca2+ release and gluconeogenesis. The action of norepinephrine, but not of glucagon, upon Ca2+ efflux is prevented by the -adrenergic antagonist, phenoxybenzamine. The action of norepinephrine is not prevented by the {beta}-adrenergic antagonist, propranolol. Together these results indicate that the release of Ca2+ from a common pool of exchangeable Ca2+ is important to the action of a variety of hormones on hepatocytes. This Ca2+ pool in the isolated hepatocyte is characterized as being similar in size and having exchange kinetics that are comparable to those reported for the major intracellular pool of Ca2+ in the intact liver. The possibility that this pool is intramitochondrial calcium is discussed.
