The rapid inhibitory effect of glucocorticoid on cytosolic free Ca2+ increment induced by high extracellular K+ and its underlying mechanism in PC12 cells

The effect of glucocorticoid(GC) on peak cytosolic free calcium net increment (deltaCa2+]i) induced by high-K+ was detected with MiraCal Image System. The main results were as follows: (1) Corticosterone(B) could inhibit deltaCa2+]i in a time-dependent and concentration-dependent manner. (2) The inhibitory effect of B could be mimicked by bovine-serum albumin conjugated corticosterone (B-BSA) also in a dose-dependent manner. (3) G-protein inhibitor, either PTX or GDP beta S significantly reduced the inhibitory effect of B and B-BSA on deltaCa2+]i (4) PMA, a stimulator for protein kinase C(PKC), could inhibit deltaCa2+]i. (5) Although the inhibitors of PKC, chelerythrine chloride and bisindolylamide I per se had no influence on deltaCa2+]i, but they significantly antagonized the inhibitory effect of B and B-BSA on deltaCa2+]i. It is postulated that GC inhibit deltaCa2+]i induced by high-K+ through a membrane mechanism and by a pathway involving G-protein and PKC.