[Effect of glucocorticoid on [Ca2+]i induced by high-K+ in single PC12 cells and its characteristics]

The effect of glucocorticoid on the increase of cytosolic free calcium [Ca2+]i) induced by high-K+ was investigated in pheochomocytoma PC12 cells. The main result was as follows: (1) When the cells were preincubated at 37 degrees C for various time intervals in the presence of 10(-5) mol/L of corticosterone and stimulated with 55 mmol/L KCl, an inhibitory effect of corticosterone on delta [Ca2+]i was observed in a time-dependent manner with maximal effect at 5th min and no effect at 25th min. (2) When PC12 cells were preincubated with various concentration of corticosterone at 37 degrees C for 5 min, the inhibitory effect of corticosterone on delta [Ca2+]i induced by 55 mmol/L KCl was concentration-dependent. The effect was found to be maximal at 10(-5) mol/L of corticosterone and disappeared at 10(-9) mol/L of corticosterone. (3) Other steroids such as cortisol, dexamethasone, progesterone, testosterone, 17 beta-estradiol and aldosterone also inhibited the rise of [Ca2+]i evoked by 55 mmol/L KCl in PC12 cells to different extents, i.e., in the rank of P = F > Dex > T > Ald = E2. Cholesterol was ineffective at the concentration up to 10(-5) mol/L for inhibiting [Ca2+]i evoked by 55 mmol/L KCl. (4) Corticosterone could not inhibit the [Ca2+]i rise induced by changing the concentration of extracellular calcium from Ca(2+)-free to 3 mmol/L.