dairy goats: Trial 1 comprised 54 goats allocated to receive two 37.5μg d-cloprostenol doses at intervals of seven (T7, n=19), 10 (T10, n=18), and 11.5 (T11.5, n=17) days. Trial 2 comprised 62 goats allocated to receive injections at T7 (n=30) and T11.5 (n=32). All females showed progesterone concentrations >1ng/mL before both d-cloprostenol injections. The largest follicle diameter present on ovaries was similar (P>0.05) among treatments at the first and second dose. The second largest follicle diameter was superior (P<0.05) to T7 than to T10 and T11.5 goats at first dose only.

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.