Comparative luteolytic effects of prostaglandin F2 alpha and its 13-dehydro analogs in vivo.

Several 13-dehydro analogs were shown to be luteolytic in both the cyclic sheep and cyclic primate models studied. The fact that these luteolytic analogs have diminished uterine smooth muscle activity suggests that the receptors governing the smooth muscle effect on the one hand, and the luteolytic effect on the other, may possess different structural specificities. In both species studied, the analogs showed marked resistance to the PG-15-OH-dehydrogenase in vivo as shown by their activity when infused intravenously. In the early pregnant monkey, the reduced luteolytic activity of the 13-dehydro analogs suggests that mCG may have a protective effect on the corpus luteum to PGs in general. Thus, the early pregnant monkey, or possibly the hCG-treated cyclic monkey, would appear to be "essential" models in the study of luteolytic agents in the primate. Finally, previous reports of termination of early pregnancy in monkeys with luteolytic PG analogs may have depended, at least in part, on their intrinsic smooth muscle activity on the uterus.