Prostaglandin E (sulproston) is neither luteolytic nor luteotrophic during the estrous cycle in the pig

Prostaglandin E₂ (Sulproston, S) can induce parturotion and luteolysis during late pregnancy in the pig. We now tested whether Sulproston is able to interfere with the duration of the pig's estrous cycle. Sulproston was given i.m. in two injections (0.008 mg/kg each) at 12-hour-intervals to ten gilts day 10, to five gilts day 14 and to five gilts day 16 of the estrous cycle. Blood was collected shortly before and up to 48 hrs after the onset of treatment; further daily blood samples were taken from a day 0 (1st day of standing heat) to the end of the cycle. Sulproston-administration did not shorten or lenghten the duration of the estrous cycle, nor were plasma-progesterone levels altered when compared to controls. In a second study five gilts received the tenfold amount in plasma-progesterone (8.52 ± 2.8 SEM ng, treatment vs. 32.95 ± 1.86 SEM ng/ml, control) occurred on day 11, which had returned by day 16 to the level of controls (19.22 ± 6.28 ng/ml vs. 26.75 ± 2.10 SEM ng/ml, respectively). No alteration in cycle length occurred. Therefore the PGE₂-analogue Sulproston - though luteolytic in late pregnancy - is neither luteolytic nor luteotrophic during the estrous cycle of the pig.