Rapid effects of steroid hormones on free intracellular calcium in T84 colonic epithelial cells.

Studies from our laboratory have demonstrated rapid (< 1 min) nongenomic activation of K+ recycling and Na+/H+ exchange by mineralocorticoids in human colonic epithelium, and studies from other laboratories have demonstrated rapid effects of aldosterone on intracellular Ca2+ concentration ([Ca2+]i) in endothelial cells. Here a rapid nongenomic effect of aldosterone on [Ca2+]i is demonstrated in the human colonic epithelial cell line T84. Aldosterone induced a rapid increase in [Ca2+]i within approximately 2 min. The rise in [Ca2+]i after aldosterone appears to result from the activation of a Ca2+ influx pathway, inasmuch as 1) no increase in [Ca2+]i was observed with aldosterone when cells were bathed in Ca(2+)-free Krebs solution and 2) emptying of the intracellular Ca2+ stores by thapsigargin was not enhanced by addition of aldosterone to extracellular Ca(2+)-free solution. In contrast, the Ca2+ response to aldosterone, in the presence of 2 mM Ca2+ in the external bathing solution, was not decreased after intracellular Ca2+ stores were emptied by thapsigargin. Other mineralocorticoid hormones increased [Ca2+]i, whereas the glucocorticoid hydrocortisone failed to increase [Ca2+]i. These results demonstrate the existence of a mineralocorticoid-specific Ca(2+)-signaling pathway in human colonic T84 (crypt) epithelial cells.