Effect of prostaglandin F-2alpha and uterine extracts on progesterone secretion in vitro by superfused pig corpora lutea.

Corpora lutea obtained from sows in the mid-luteal phase of the oestrous cycle were superfused with various doses of PGF-2alpha, uterine flushings or superfusates from endometrial strips. High doses of PGF-2alpha (1-5 microgram/ml) gave transient stimulation of progesterone secretion; lower doses (0.1-1.0 microgram/ml) inhibited secretion of the steroid, but to a maximum of 55% only and the secretion returned to control levels when superfusion with PGF-2alpha stopped. Uterine flushings from sows in the late luteal phase of the cycle were more effective than mid-cycle flushings in inhibiting progesterone secretion by the luteal tissue: maximal inhibition was 65% and progesterone secretion slowly returned to control levels when superfusion with the flushings was stopped. Superfusate from strips of uterine endometrium from sows in the late luteal phase of the cycle proved most effective in inhibiting progesterone secretion (greater than 90%) and gave a long-lasting inhibition which did not appear to be due to stimulation of PGF-2alpha secretion by the endometrium or corpus luteum.