Intraluminally infused prostaglandins induce jejunal secretion of water and electrolytes in man, and a receptor-mediated process in the intestinal epithelial cells has been suggested to explain this secretion. In an attempt to obtain data under basal conditions for pharmacological studies, we tested the dose-response effect of PGE1 on jejunal hydroelectrolytic movements in 10 healthy volunteers. 2. Accordingly, a solution with or without PGE1 was infused via a four-lumen tube with a proximal occluding balloon and jejunal water and electrolyte transport were determined. The segment tested was 40 cm long. Seven randomized doses of PGE1 ranging from 0.01 to 1.3 micrograms kg-1 min-1 (2.83 to 364 pmol kg-1 min-1) were infused in an isotonic control saline solution. The secretion induced by PGE1 was evaluated in each subject as the difference between fluxes in response to the control saline solution and to PGE1. 3. Whatever the dose, PGE1 induced secretion of water, Na+, K+ and Cl- which was dose-dependent and saturable, with a mean Km of congruent to 6-8 pmol kg-1 min-1, suggesting that at the pharmacological doses used, enterocytes have a saturable membrane site similar to a single class of receptor for PGE1. 4. These findings may be of great importance if prostaglandins are administered as drugs or used as jejunal secretory agents in vivo when the antisecretory effect of another drug is studied.
