Lee A. Edgerton

Effects of progesterone and estradiol-17 beta on uterine secretion of prostaglandin F2 alpha in response to oxytocin in ovariectomized ewes.

Abstract Thirty ovariectomized sows were used in an experiment designed to determine whether the ability of the porcine uterus to release prostaglandin (PG) F2α in response to oxytocin is regulated by progesterone (P4) and estradiol (E2). Sows were assigned to one of four treatment groups: 1) no steroids (ovariectomized controls; n = 8), 2) E2 (n = 8), 3) P4 (n = 7), or 4) E2 + P4 (n = 7). P4 and E2 were administered so as to mimic the normal temporal changes that occur in these hormones during the estrous cycle. A group of intact sows (n = 9) was included for comparison. All sows received an injection of oxytocin (30 IU, i.v.) on Days 12, 15, and 18 postestrus. Jugular venous blood samples were collected from 60 min before through 120 min after injection of oxytocin for quantification of 13,14-dihydro-15-keto-PGF2α (PGFM). Preinjection baseline concentrations of PGFM, the magnitude of the PGFM response above baseline, and area under the PGFM response curve (AUC) were calculated for each sow on each day and compared among treatment groups by ANOVA. Among the ovariectomized sows receiving steroid replacement, baseline concentrations of PGFM were low on Day 12 postestrus in all four groups. On Days 15 and 18, baseline concentrations remained low in the two groups that did not receive P4 but increased in those that did. Both the magnitude of the response to oxytocin and AUC were small on Day 12 postestrus in all 4 groups. By Day 15, the magnitude of the response and AUC increased in the group that received both P4 and E2 but remained low in the other three groups. By Day 18, responses to oxytocin were greater in both groups that received P4 than in those that did not. Baseline concentrations were similar in intact sows and in those that received both P4 and E2 on all three days examined. The magnitude of the response and the AUC were greater in the ovariectomized sows receiving P4 and E2 replacement than in the intact control sows on Days 15 and 18 postestrus. From these results, we conclude that P4 and E2 interact to control the time when the uterus begins to secrete PGF2α in response to oxytocin and the amount of PGF2α secreted.

Effects of estrogen and prostaglandin on progesterone-delayed farrowing

Effects of estradiol benzoate and prostaglandin F(2alpha) (PGF(2alpha)) on concentrations of progesterone and estrogen in serum and the percentage of live births were determined in 21 gilts treated with exogenous progesterone in late gestation. All gilts received progesterone (25mg s.c. four times daily) from Days 108 through 113 of gestation. Gilts receiving no other treatments (controls) had elevated levels of progesterone through 1800 h on Day 114 (29.2 +/- 11.4 ng/ml) and farrowed at 115.6 +/- 0.3 d of gestation with a relatively low percentage of live births (66.8 +/- 17.3). Gilts treated with PGF(2alpha) administered at 0600 h on Day 114 had less (P<0.01) progesterone by 1800 h (7.0 +/- 1.3 ng/ml) relative to that of the controls, but they had similar gestation lengths (115.5 +/- 0.3) and percentages of live births (50.0 +/- 16.2). Administration of estradiol benzoate (10 mg) to gilts at 0600 h on Day 114 did not reduce progesterone on Day 114 or the gestation length relative to that of the control gilts, but it did increase (P<0.05) the percentage of live births (100%).

Serum progesterone and luteinizing hormone following prostaglandin F2α during the sow's estrous cycle

Abstract Thirty-six sows and gilts (hereafter called sows) received one of three prostaglandin F2α(PGF2α) treatments on day 6, 10, or 14 of the estrous cycle to determine the effect of prostaglandin treatment on subsequent concentrations of luteinizing hormone (LH) and progesterone. Also, the effect of treatment on estrous cycle lengths was evaluated. Blood was sampled every 15 min for 6 h. Starting from time 0, sows received 25 mg of PGF2α at 4 h (treatment 1), 50 mg at 4 h (treatment 2), or 25 mg at both 1 h and 4 h (treatment 3). Treatment and day of cycle that sows were treated modified estrous cycle lengths (P 0.05) among the three cycle stages nor altered by quantity of PGF2α although the response to a second injection (treatment 3) was diminished (P 0.05) at any time. Therefore, it appears that resistance of naturally occurring corpora lutea (of the estrous cycle) in swine to the luteolytic action of PGF2α is not due to gonadotropic support from the pituitary.

Estrogen-induced delay of farrowing in swine

Abstract Eighty-four sows and gilts were assigned to 4 treatment groups to assess the effects of estrogen upon normal and prostaglandin-induced farrowing. Sows in Group 1 were injected with saline and corn oil vehicles at 800 hours on Day 112 of gestation and served as controls. Sows in Group 2 received saline and 3 mg of estradiol benzoate. Sows in Group 3 received 10 mg of prostaglandin F2α (PGF2α) and corn oil, and sows in Group 4 received both the PGF2α and estradiol benzoate. The control sows farrowed at 74.5 ± 6.8 hours after vehicle injections. Surprisingly, the average time from treatment to onset of parturition was significantly increased (P 0.1). Performance characteristics of estrogen-treated sows and their litters were equal to those of the control sows.