Relationship of Prostaglandin F2α to Cystic Ovarian Follicles in the Sow

Abstract

Large multiple cystic ovarian follicles were induced in six sows and small multiple cystic ovarian follicles were induced in five other sows by daily injections of adrenocorticotrophic hormone (ACTH) during the follicular phase of the oestrous cycle. Sows with large cysts had elevated levels of plasma oestradiol that fluctuated considerably to peaks of 60 pg/ml. Plasma progesterone values were also raised and varied between 5 and 15 ng/ml. In sows with small cysts, plasma oestradiol concentrations ranged between 10 and 20 pg/ml while progesterone values were less than 5 ng/ml, except for one sow with coincident corpora lutea. Spontaneous degeneration of large cystic follicles was associated with an elevation in peripheral plasma values (400 to 600 pg/ml) of 13, 14-dihydro-15-keto-prostaglandin F 2α (PGFM) for several days and was accompanied by a sharp decline in oestradiol and progesterone values. Prostaglandin F 2α (PGF 2α ) was measured in utero-ovarian vein blood in one sow at this time and values between 1000 and 2500 pg/ml were present. In one sow with large cysts hysterectomy was performed to prevent endogenous production of PGF 2α and in a second sow large cysts occurred spontaneously. Intramuscular injection of PGF 2α into these two animals resulted in degeneration of the large cystic follicles. In three of the sows with small multiple cysts, studied for up to 30 days, spontaneous degeneration did not occur and PGFM values remained low. Injection of PGF 2α into the other two sows with small cysts appeared to have no effect on these cystic follicles. The results suggest that large multiple ovarian cysts are able to respond to PGF 2α of endogenous or exogenous origin by degeneration in a manner somewhat analogous to normal luteolysis. Sows with small multiple cystic follicles do not seem to produce PGF 2α endogenously and appear to be unresponsive to PGF 2α injected intramuscularly.