A role for Na+-K+-activated adenosine triphosphatase (Na-K-ATPase) in intestinal sodium and water absorption under basal conditions has not been demonstrated in vivo. To delineate this role, adjacent rabbit ileal loops were simultaneously perfused in vivo with a Ringer-HCO3 solution. The perfusate was then changed in one of the loops to a Ringer-HCO3 solution containing ouabain. After the perfusion, each loop was assayed for Na-K-ATPase and Mg-ATPase activities. Perfusion with 19.2 mM ouabain produced net sodium and water secretion and a 32% reduction in Na-K-ATPase activity. Ouabain perfusion did not alter the activity of Mg-ATPase or affect histology. When a Ringer-HCO3 solution containing 15 mM glucose was perfused, ouabain reduced glucose absorption by 50%. As predicted from the known competition between ouabain and potassium for a Na-K-ATPase receptor site in vitro, ouabain-induced intestinal secretion and Na-K-ATPase inhibition could be reversed with a Ringer-HCO3 solution containing 25 mM KCl. These results suggest that: mucosal Na-K-ATPase plays an important role in the ileal absorption of sodium, glucose, and water under basal conditions; and that an underlying intestinal secretory process exists as revealed by the selective in vivo inhibition of intestinal absorption.
|Original language||English (US)|
|Journal||American Journal of Physiology Endocrinology Metabolism and Gastrointestinal Physiology|
|State||Published - 1978|
ASJC Scopus subject areas