[Release of an endogenous Na+, K+-ATPase into the blood during hypoosmotic stimulation of the mucosa of the gastrointestinal tract in rats].

An endogenous activator (EA) of Na+, K(+)-ATPase was found in the rat blood serum in the in vivo experiments. EA appeared after intragastric introduction of mannitol hypotonic (20 mmol/l) solution (1.5% b. w.) and activated enzyme of the intact rat enterocytes. EA retained its effect on Na+, K(+)-ATPase after heating during 10 min up to 100 degrees C. This endogenous activator is thermally stable and belongs to low molecular compounds with the molecular weight of 10 kDa. It is supposed that EA can participate in the water-salt humoral regulation after loading the organism with hypoosmotic solutions.