[Effect of intestinal circulation on the osmotic balance between the intestinal lumen and blood in awake rats].

Total electrolyte concentrations in portal vein and aortic blood of unanesthetized rats were measured continuously by means of ultrafiltrate conductometry. Portal flow rate and mesenteric venous pressure (pmes) could also be measured. The last could be raised to any desired level by a specially developed portal vein clamp. Intraduodenal injections of water (0.5 or 1% BW) were given in a first series of experiments with and without sham-attacking (activating) the animal for 10 s and in a second series with and without raising pmes. Portal flow rate dropped in both cases. But whereas activation led to a decrease in the concentration changes in the v. portae and in arteriovenous differences, a rise in pmes had the opposite effect. Comparison of the total free water change in the v. portae (Mpo) with the quantity of water given (MH2O) revealed that Mpo/MH2O dropped in both series of experiments, provided that pmes was not increased by much more than 2 mm Hg (portal flow did not decrease much under normal). The differing results were explained by taking into account the specificities of blood circulation in the gut wall. The experiments have shown that even transient obstruction of gut tissue perfusion can delay dissipation of concentration imbalance between the gut and parenteral space, thus having adverse effects on the gut cells.