[Osmotic actions on the epithelial Na,K pump of the small intestine].

Intragastric administration of mannitol or NaCl hypotonic solution induced a significant shift of the electrolyte balance in the small intestine epithelium, and activated the enterocytes' Na,K pump in Wistar rats. De-ionised water caused the maximal enhancement of the Na,K-ATPase activity, whereas hypertonic solutions exerted the opposite effect, a substance-inhibitor appearing in the blood serum. Similar results were obtained in vitro. The possibility of the Na,K-pump regulation by enterocytes and the role of small intestine in secretion of an endogenous factor regulating this enzyme's activity, is discussed.