EFFECTS OF PROSTAGLANDIN F-2-ALPHA' CLOPROSTENOL AND FENPROSTALENE ONUTERINE CLEARANCE OF RADIOCOLLOID IN THE MARE

Uterine clearance of radiocolloid was measured by scintigraphy in 5 re productively 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 t hird day of estrus during 3 consecutive estrous cycles. Drugs, PGF(2 a lpha) (5 mg IM), cloprostenol (CLO; 2mg IM) or fenprostalene (FEN; 250 mu g subcutaneously) were given in random order, with only 1 drug giv en each estrus. Treatment response curves were generated, and the effe ct of each drug on uterine clearance of radiocolloid was compared to t he clearance of radiocolloid when no drug was given and between treatm ents. In reproductively normal mares, CLO and PGF caused a rapid clear ance of radiocolloid within 60 min (P < 0.01), with < 25% of the initi al 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 repr oductively 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 treat ment with CLO at 60 and 120 min than after PGF (P < 0.001). In conclus ion, CLO appears to be the best drug of the 3 tested for stimulating c learance of intrauterine fluid since variation in response was observe d following treatment with PGF and FEN.