HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Gardner, J. P. Articles by Zhang, L. Search for Related Content PubMed PubMed Citation Articles by Gardner, J. P. Articles by Zhang, L.

Glucocorticoid modulation of Ca²⁺ homeostasis in human B lymphoblasts

Jeffrey P. Gardner * and Li Zhang

We determined the effect of cortisol (200 nM for 48 h) on the intracellular Ca²⁺ concentration ([Ca²⁺]_i) and parameters of Ca²⁺_i signalling in 19 lymphoblastoid cell lines (LCLs).

Using the fluorescent dye fura-2, the basal [Ca²⁺]_i in Ca²⁺-containing medium was 63·5 ± 2·4 nM in vehicle (ethanol)-treated LCLs and 55·7 ± 2·6 nM (mean ± s.e.m.) in cortisol-treated LCLs.

Ca²⁺_i signalling following platelet-activating factor (PAF, 100 nM) addition was enhanced by cortisol treatment, with LCLs having small PAF responses showing the largest percentage increase after cortisol treatment. Mean peak [Ca²⁺]_i responses to PAF were enhanced 67·0 % and 55·7 % in Ca²⁺-free and Ca²⁺-containing medium, respectively.

The endoplasmic reticulum Ca²⁺-ATPase inhibitor thapsigargin (100 nM) caused a transient increase in [Ca²⁺]_i in Ca²⁺-free medium in which the peak change was increased in cortisol-treated cells (98·5 ± 5·8 vs. 79·8 ± 4·5 nM). Peak changes in the freely exchangeable Ca²⁺ in response to 5 µM ionomycin were also enhanced in cortisol-treated cells (923·7 ± 113·9 vs. 652·2 ± 64·5 nM) and correlated to the PAF-evoked [Ca²⁺]_i response.

Cortisol-treated LCLs exposed to thapsigargin to empty intracellular Ca²⁺ stores (10 min treatment in Ca²⁺-free medium) and exposed to CaCl₂ or MnCl₂ had a greater rate of Ca²⁺ entry (18·6 ± 1·8 vs. 13·8 ± 1·5 nM s^-1) and higher rate constant for Mn²⁺ entry (0·0345 ± 0·0029 vs. 0·0217 ± 0·0020) than vehicle-treated cells. Peak [Ca²⁺]_i in cells exposed to CaCl₂ was also enhanced (869·4 ± 114·7 vs. 562·6 ± 61·7 nM). Parameters of divalent cation influx were highly correlated to the peak [Ca²⁺]_i elicited by thapsigargin or ionomycin.

Inclusion of RU 486 (a glucocorticoid antagonist) with cortisol prevented the decrease in basal [Ca²⁺]_i and stimulatory actions of cortisol on all Ca²⁺_i parameters. RU 486 alone had no apparent effects on basal [Ca²⁺]_i or Ca²⁺_i signalling.

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 [Ca²⁺]_i and enhances PAF-evoked [Ca²⁺]_i signalling, most probably through its effects on intracellular Ca²⁺ stores. In turn, the extent of Ca²⁺ entry via store-operated plasma membrane Ca²⁺ channels is closely linked to the size of the Ca²⁺ stores.

This article has been cited by other articles:

				S. Greenstein, K. Ghias, N. L. Krett, and S. T. Rosen Mechanisms of Glucocorticoid-mediated Apoptosis in Hematological Malignancies Clin. Cancer Res., June 1, 2002; 8(6): 1681 - 1694. [Abstract] [Full Text] [PDF]