Effect of dexamethasone on electrolyte transport in the large intestine of the rat

Abstract

We examined the effect of glucocorticosteroids on fluid and electrolyte movement in the rat colon. Dexamethasone, 600 μg per 100 g of body weight daily for 3 days, significantly increased water and sodium absorption, potassium secretion, the electrical potentional difference (PD), and Na-K-ATPase activity. Significant increases in PD and Na-K-ATPase activity were also produced by doses of dexamethasone (10 and 25 μg per 100 g of body weight, respectively) that more closely approximate a physiological dose. Further, the increase in PD was observed as soon as 3 hr after dexamethasone administration and persisted for 24 to 48 hr. Five hours after the administration of dexamethasone, Na-K-ATPase activity was not increased despite significant increments in Na absorption, K secretion, and PD. Dexamethasone increased fluid and sodium absorption during both saline and deoxycholic acid perfusions. In contrast to the net water and sodium secretion in the control group during bile acid perfusions, net absorption was present in the dexamethasone-treated animals. These studies extend previous observations of the effect of glucocorticoids on water and electrolyte movement in the large intestine and provide data concerning the minimal dose and time course of the interaction of glucocorticoids with ion transport. These observations indicate that glucocorticoids may provide important regulatory control of colonic ion transport, and that the mechanism of these glucocorticoid effects is not mediated by Na-K-ATPase.