Effects of prostaglandin F-2 alpha' cloprostenol and fenprostalene on uterine clearance of radiocolloid in the mare

Uterine clearance of radiocolloid was measured by scintigraphy in 5 reproductively normal mares and in 4 mares exhibiting a delay in uterine clearance (DUG) after administration of PGF(2 alpha), cloprostenol or fenprostalene. Scintigraphy studies were performed on the second or third day of estrus during 3 consecutive estrous cycles. Drugs, PGF(2 alpha) (5 mg IM), cloprostenol (CLO; 2mg IM) or fenprostalene (FEN; 250 mu g subcutaneously) were given in random order, with only 1 drug given each estrus. Treatment response curves were generated, and the effect of each drug on uterine clearance of radiocolloid was compared to the clearance of radiocolloid when no drug was given and between treatments. In reproductively normal mares, CLO and PGF caused a rapid clearance of radiocolloid within 60 min (P < 0.01), with < 25% of the initial dose of radiocolloid (% IDR) remaining by 120 min. Mean percentage of IDR at 120 min when no drug was given was 39%+/-4. Response of reproductively normal mares to FEN varied, with 3 mares clearing >85% and 2 mares clearing <35%. In mares exhibiting DUG, all 3 drugs (CLO, PGF and FEN) caused rapid clearance of radiocolloid from the uterus by 60 min (P < 0.0001). Mares cleared significantly more colloid after treatment with CLO at 60 and 120 min than after PGF (P < 0.001). In conclusion, CLO appears to be the best drug of the 3 tested for stimulating clearance of intrauterine fluid since variation in response was observed following treatment with PGF and FEN.