Specific binding of dl-cloprostenol and d-cloprostenol to PGF2 alpha receptors in bovine corpus luteum and myometrial cell membranes

Prostaglandin F2 alpha receptors (PGF2 alpha Rs) were measured in bovine corpus luteum and myometrial cell membranes using a radiometric method. The inhibition of labelled PGF2 alpha binding exerted by d-cloprostenol, dl-cloprostenol, PGF2 alpha and PGE1 (10(-11) M to 10(-4) M) was evaluated in vitro. Results strongly suggest that cloprostenol binding to PGF2 alpha Rs is stereospecific. d-Cloprostenol and PGF2 alpha were equipotent, about 150 times more potent than dl-cloprostenol (P < 0.05) and approximately 280 times more potent than PGE1 (P < 0.05) in inhibiting [3H]PGF2 alpha binding to corpus luteum cell membranes. Such differences were less evident in myometrial cell membranes, where d-cloprostenol and PGF2 alpha were about 10 times more potent than dl-cloprostenol (P < 0.05) and approximately 95 times more potent than PGE1 (P < 0.05).