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Glucocorticoid modulation of Ca 2+ homeostasis in human B lymphoblasts
Author(s) -
Gardner Jeffrey P.,
Zhang Li
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.385ae.x
Subject(s) - thapsigargin , ionomycin , fura 2 , medicine , endocrinology , intracellular , glucocorticoid , endoplasmic reticulum , chemistry , homeostasis , lymphoblast , calcium , cell culture , biophysics , biology , cytosol , biochemistry , enzyme , genetics
1 We determined the effect of cortisol (200 n m for 48 h) on the intracellular Ca 2+ concentration ([Ca 2+ ] i ) and parameters of Ca 2+ i signalling in 19 lymphoblastoid cell lines (LCLs). 2 Using the fluorescent dye fura‐2, the basal [Ca 2+ ] i in Ca 2+ ‐containing medium was 63.5 ± 2.4 n m in vehicle (ethanol)‐treated LCLs and 55.7 ± 2.6 n m (mean ± s.e.m. ) in cortisol‐treated LCLs. 3 Ca 2+ i signalling following platelet‐activating factor (PAF, 100 n m ) addition was enhanced by cortisol treatment, with LCLs having small PAF responses showing the largest percentage increase after cortisol treatment. Mean peak [Ca 2+ ] i responses to PAF were enhanced 67.0% and 55.7% in Ca 2+ ‐free and Ca 2+ ‐containing medium, respectively. 4 The endoplasmic reticulum Ca 2+ ‐ATPase inhibitor thapsigargin (100 n m ) caused a transient increase in [Ca 2+ ] i in Ca 2+ ‐free medium in which the peak change was increased in cortisol‐treated cells (98.5 ± 5.8 vs. 79.8 ± 4.5 n m ). Peak changes in the freely exchangeable Ca 2+ in response to 5 μ m ionomycin were also enhanced in cortisol‐treated cells (923.7 ± 113.9 vs. 652.2 ± 64.5 n m ) and correlated to the PAF‐evoked [Ca 2+ ] i response. 5 Cortisol‐treated LCLs exposed to thapsigargin to empty intracellular Ca 2+ stores (10 min treatment in Ca 2+ ‐free medium) and exposed to CaCl 2 or MnCl 2 had a greater rate of Ca 2+ entry (18.6 ± 1.8 vs. 13.8 ± 1.5 n m s −1 ) and higher rate constant for Mn 2+ entry (0.0345 ± 0.0029 vs. 0.0217 ± 0.0020) than vehicle‐treated cells. Peak [Ca 2+ ] i in cells exposed to CaCl 2 was also enhanced (869.4 ± 114.7 vs. 562.6 ± 61.7 n m ). Parameters of divalent cation influx were highly correlated to the peak [Ca 2+ ] i elicited by thapsigargin or ionomycin. 6 Inclusion of RU 486 (a glucocorticoid antagonist) with cortisol prevented the decrease in basal [Ca 2+ ] i and stimulatory actions of cortisol on all Ca 2+ i parameters. RU 486 alone had no apparent effects on basal [Ca 2+ ] i or Ca 2+ i signalling. 7 Based on data obtained over a wide range of responses (in the presence and/or absence of cortisol or RU 486), the results show that cortisol stimulation of glucocorticoid receptors decreases basal [Ca 2+ ] i and enhances PAF‐evoked [Ca 2+ ] i signalling, most probably through its effects on intracellular Ca 2+ stores. In turn, the extent of Ca 2+ entry via store‐operated plasma membrane Ca 2+ channels is closely linked to the size of the Ca 2+ stores.