Corpus luteum regression induced by ultra-low pulses of prostaglandin F2 alpha.

In view of the pulsatile nature of PGF2 alpha secretion from the ovine uterus at the time of luteolysis, experiments were designed to examine the effect of pulsed infusions of PGF2 alpha on luteal function and to re-examine the minimal effective levels of PGF2 alpha required to induce luteolysis. To mimic physiological conditions, hour-long infusions of PGF2 alpha in increasing concentrations were given either 4 times in 19 h or 5 times in 25 h into the arterial supply of the autotransplanted ovary in conscious sheep on day 12 of an induced cycle. Blood flow and progesterone secretion rate from the ovary were used to monitor directly the luteolytic effect of administered PGF2 alpha.

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.