Na+-K+-activated adenosine triphosphatase and intestinal electrolyte transport. Effect of adrenal steroids.

Abstract

A B S T R A C T Sodium-potassium-activated adenosine triphosphatase (Na-K-ATPase) is associated with electrolyte transport in many tissues. To help delineate its role in intestinal transport, changes in rat intestinal electrolyte and water transport induced by injecting methylprednisolone acetate 3 mg/100 g or deoxycorticosterone acetate (DOCA) 0.5 mg/100 g per day for 3 days were correlated with changes in Na-K-ATPase activity. Methylprednisolone increased sodium and water absorption, potassium secretion, transmural potential difference, and Na-K-ATPase activity in the jejunum, ileum, and colon. Examination of isolated epithelial cells demonstrated that the jejunal and ileal increase in Na-K-ATPase occurred in both the villus tip and crypt areas. The time-courses of the ileal enzyme and transport changes were identical. Permeability, Mg-ATPase, and adenylate cyclase activities were unchanged by methylprednisolone. DOCA increased sodium and water absorption, potassium secretion, transmural potential difference, and Na-K-ATPase activity in the colon alone. Colonic Mg-ATPase and adenylate cyclase activities were unaffected. Jejunal and ileal enzyme activity, electrolyte transport, and permeability were unchanged by DOCA. Methylprednisolone and DOCA were not additive in their effect on colonic Na-K-ATPase activity. Methylprednisolone and DOCA increased electrolyte and water transport and Na-K-ATPase activity concomitantly in specific segments of small intestine and colon. These data are consistent with an important role for Na-K-ATPase in intestinal electrolyte and water transport.

Stimulation of hepatic sodium and potassium-activated adenosine triphosphatase activity by phenobarbital. Its possible role in regulation of bile flow.

“…(Na+-K+)-ATPase is present in the surface membrane of most cells (25) and has been shown to adapt to increased sodium loads (43,44), glucocorticoids (45,46), and thyroid hormone (21,47). The tissue specificity of phenobarbital induction was therefore examined in the small intestine, kidney, and skeletal muscle.…”

Glucocorticoid Activation of Na+/H+Exchanger Isoform 3 Revisited

“…Although in some of these circumstances the antidiarrheal effects of glucocorticoids may result from the direct effect on processes underlying the diseases, it is widely accepted that glucocorticoids have a direct effect on intestinal salt and water absorption. The fact that glucocorticoids have a direct effect on intestinal salt and water absorption has been known for more than two decades (2,6). Pharmacologic doses of methylprednisolone have been shown to increase Na ϩ , Cl ϩ , and water absorption in vivo in both small intestine and colon of the rat.…”

Glucocorticoids and the Intestinal Environment

“…The effects of mineralocorticoids and glucocorticoids on intestinal water and ion movements are well known. Methylprednisolone for 3 days increased Na + K + adenosinetriphosphatase activity and Na + absorption [83]; it also increased guanylate cyclase activity and Cl -secretion in the jejunum and ileum 6 h after administration [84,85]. However, there is no direct information about the increase of water and ion secretion related with increased glucocorticoid secretions in different stressful conditions.…”