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Acta Physiologica 2012; Volume 204, Supplement 689
91st Annual Meeting of The German Physiological Society
3/22/2012-3/25/2012
Dresden, Germany
ROLE OF THE SERUM-AND-GLUCOCORTICOID-INDUCED PROTEINKINASE (SGK) IN THE REGULATION OF THE CARDIAC L-TYPE CA2+ CURRENT BY INSULIN AND CORTICOSTEROIDS
Abstract number: P188
Wagner1 *M., Mansley1 M., Schauer1 A., Friedrich1 C., Volk1 T.
1FAU Erlangen-Nrnberg, Institut fr Zellulre und Molekulare Physiologie, Erlangen, Germany
Corticosteroids have been shown to increase the L-type Ca2+ current (ICaL) in cardiomyocytes in vitro by activation of the mineralocorticoid receptor (MR). The signal transduction pathways involved, however, are incompletely understood. Here we demonstrate that the upregulation of ICaL depends on the presence of insulin or IGF-1 and is sensitive to inhibition of the phosphatidylinositol 3-kinase (PI3-K) or the serum-and-glucocorticoid-induced proteinkinase (SGK-1). Left ventricular cardiomyocytes were isolated from female Wistar rats and investigated by the whole-cell patch-clamp technique after 24h incubation with corticosteroids alone, in combination with insulin or IGF-1 and/or in the presence of inhibitors of PI3-K or SGK-1. In the presence of 100nM insulin, dexamethasone (1mM) increased ICaL (at 0mV) by 49% from 8.2±0.6 pApF-1 (n=15) to 12.2±0.9 pApF-1 (n=15, p-1, n=11). Co-incubation with 1mM dexamethasone and 10nM IGF-1 increased ICaL by 42% (pCaL after 24h. Concentration-response relations revealed an EC50 of 0.43nM and 4.7nM for IGF-1 and insulin, respectively. Similarly, incubation with aldosterone increased ICaL in the presence of insulin but not in its absence. Coincubation with the PI3-K inhibitors PI-103 (0.5mM) or LY294002 (50mM) as well as coincubation with the SGK inhibitor GSK650394 (10mM) abrogated the dexamethasone/insulin-induced effect on ICaL, while in the absence of dexamethasone/insulin, the inhibitors did not alter ICaL. GSK650394 (10mM) did not affect the activity of PKB/Akt in isolated cardiomyocytes incubated with dexamethasone/insulin after 24h as assessed by the degree of phosphorylation of the PKB/Akt specific substrate filamin-C. We conclude that corticosteroids and insulin/IGF-1 synergistically induce the increase in ICaL and may constitute important cofactors in the regulation of cardiac function under physiological and pathophysiological conditions.
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Acta Physiologica 2012; Volume 204, Supplement 689 :P188