E-type prostaglandin binding sites in isolated canine parietal cells: elucidation with (3H) misoprostol free acid.

(3H) Misoprostol free acid, a prostaglandin E1 analog, was used to identify high affinity binding sites for E-type prostaglandins in enriched canine parietal cell preparations. Saturable, reversible, and highly stereospecific binding, with an estimated number of 8000 binding sites per cell, was demonstrated. The binding sites have high affinity for misoprostol, misoprostol free acid, and other E-type prostaglandins. Prostaglandins of the I- and F-type bind weakly, and chemically unrelated compounds, such as histamine and cimetidine, do not bind. The results indicate that (3H) misoprostol free acid binds to E-type prostaglandin receptors, and that the ulcer-healing drug, misoprostol, inhibits gastric acid secretion through interaction with a specific E-type prostaglandin receptor.