EFFECTS OF LOW-DOSES OF PROSTAGLANDIN-F2-ALPHA DURING THE EARLY LUTEAL-PHASE BEFORE AND AFTER IMPLANTATION IN BEAGLE BITCHES

Three groups of five beagle bitches were treated three times a day wit h natural prostaglandin F-2 alpha (PGF(2 alpha)) at a dosage of either 20 mu g kg(-1) bodyweight (days 5-8 of metoestrus), 50 mu g kg(-1) bo dyweight (days 5-11 of metoestrus) or 20 mu g kg(-1) bodyweight after detection of pregnancy (days 20-21 after ovulation) for 7 days. A dose of 20 mu g PGF(2 alpha) kg(-1) bodyweight administered during the ear ly luteal stage could not induce a reliable decrease of progesterone c oncentrations, while injections of 50 mu g PGF(2 alpha) kg(-1) bodywei ght beginning before implantation resulted in arrest of luteal progest erone production and prevention of nidation in all five bitches. The a pplication of 20 mu g PGF(2 alpha) kg(-1) bodyweight shortly after imp lantation induced functional arrest of corpora lutea and led to embryo nic or fetal resorption in all cases. In general, the luteolytic effec t of low PGF(2 alpha) doses was insufficient because of the recovery o f the corpora lutea seen in nearly all bitches and the prolonged proce ss of embryonic or fetal resorption that increase the risk of uterine disease.