Effect of the uterus on induced cystic ovarian follicles in the sow.

Large multiple cystic ovarian follicles were induced in 16 sows and small multiple cystic ovarian follicles were induced in five sows by daily injections of adrenocorticotrophic hormone during the follicular phase of the oestrous cycle. Large ovarian cysts persisted until euthanasia at 35 to 51 days after complete bilateral hysterectomy between days 5 and 10 in four sows. Atresia of large cysts was seen about days 15-18 in a sham-hysterectomy experiment. Unilateral hysterectomy of three sows resulted in persistence of large cysts on the ovary adjacent to uterine horn removal and atresia in the contralateral ovary. Lutein patches developed on the follicular wall of persistent cysts between the time of hysterectomy and autopsy. Atresia did not occur after hysterectomy in three sows with small cystic follicles, nor did sham hysterectomy of a sow with small ovarian cysts result in cyst atresia. A pronounced reduction in the size of large cysts occurred in three of four sows after the intrauterine injection of prostaglandin F2a. When a prostaglandin inhibitor, indomethacin, was injected into one uterine horn, the adjacent ovarian cysts persisted while those on the ovary next to the uterine horn receiving saline solution underwent atresia. Daily urinary oestrogen values from a hysterectomised sow with large cysts were initially high but subsequently fell to values between 30 and 60 microng/ml, except for several high values when signs of oestrus were observed. Oestrogen values in urine from a hysterectomised sow with small cysts were comparatively lower, and rose to high values only once in the 50-day period studied. Plasma oestrogen values in a hysterectomised sow with large cysts were high, although considerable day-to-day variation occurred. Plasma progesterone values were also high in this sow. In a sow with small cystic follicles for a 50-day period, oestrogen values in plasma were relatively low, but higher values were obtained occasionally. Plasma progesterone levels remained consistently low in this sow.