D.L. Vincent

Reproductive hormone secretions and first service conception rate subsequent to ovulation control with Synchro-Mate B.

Two groups of beef females receiving suboptimal energy diets were treated with Synchro-Mate B to control ovulation. The first group consisted of 30 suckled cows and 16 heifers. These females were bled 10 days and immediately prior to the implantation of norgestomet implants, at implant removal, 24, 27, 30, 33 and 36 hours and 9 and 16 days post-implant removal. The second group which consisted of 40 cows and 8 heifers was handled in the same manner except no blood samples were collected from 24 to 36 hours following implant removal. Calves were removed from all the cows for 48 hours, beginning at implant removal. All animals were artifically inseminated 48 hours following implant removal. Blood plasma was assayed for concentrations of progesterone and LH. The first service conception rate was 21% and 40% for groups 1 and 2. Several factors were identified that reduced the first service conception rate. In summary, Snychro-Mate B is an effective method to synchronize estrus in cattle. However, stress subsequent to implant removal should be avoided in order to obtain a higher first service conception rate.

PGE1 or PGE2 not LH Regulates Secretion of Progesterone in Vitro by the 88-90 Day Ovine Corpus Luteum of Pregnancy

Secretion of progesterone in vitro by mature day 8 ovine corpora lutea (CL) of the estrous cycle was increased linearly by ovine LH (1, 10 and 100 ng/ml) or prostaglandin E2 (PGE2) 1, 10 and 100 ng/ml) in a dose dependent manner (P < or = 0.05). Progesterone secretion in vitro by 88-90 day ovine CL of pregnancy was not affected P > or = 0.05 by LH (1, 10 and 100 ng/ml) while prostaglandin E1 (PGE1) 1, 10 and 100 ng/ml) increased (P < or = 0.05) secretion of progesterone in a dose dependent manner and PGE2 (1, 10 and 100 ng/ml) increased (P < or = 0.05) secretion of progesterone only at the 100 ng/ml dose. Day 8 ovine CL of the estrous cycle did not secrete (P > or = 0.05) detectable quantities of prostaglandin F2 alpha (PGF2 alpha) or prostaglandin E (PGE) while 88-90 day ovine CL of pregnancy secrete PGE (P < or = 0.05) but not PGF2 alpha (P > or = 0.05). Regulation of PGE secretion by 88-90 day ovine CL of pregnancy may be via pregnancy specific protein B (PSPB), which increased (P < or = 0.05) PGE and progesterone but not PGF2 alpha (P > or = 0.05) secretion. Secretion of progesterone by CL of 88-90 days of pregnancy was not affected by IGF1, IGF2, PAF-16, PAF-18, oxytocin, PGI2, PGD2 or leukotriene C4 (P > or = 0.05). It is concluded that PGE1 or PGE2 but not LH regulates secretion of progesterone in vitro by 88-90 day ovine CL of pregnancy. In addition, it is concluded that 88-90 day ovine CL of pregnancy secretes its own luteotropin, which is PGE. Secretion of PGE by ovine CL of pregnancy may be regulated by PSPB.

Aspects of regulation of uterine secretion of prostaglandins during the oestrous cycle and early pregnancy

Abstract Evidence that the pattern of secretion of prostaglandin E 2 (PGE 2 ) by the uterus: conceptus unit is consistent with that compound playing a role in the local antiluteolytic effect of the embryo is reviewed briefly. Utero-ovarian venous concentrations of PGE 2 increased on day 13 in pregnant compared to non-pregnant ewes, both absolutely and in relation to prostaglandin F 2α (PGF 2α ). The roles of oestrogen and progesterone in regulation of utero-ovarian venous concentrations of PGF 2α were examined during two intervals of the oestrous cycle and on day 13 of the cycle or pregnancy. The first interval (Experiment l, days 10 to 14) was chosen to study the initial rises of PGF 2α that precede luteolysis. At laparotomy on day 9, a catheter was inserted into a utero-ovarian vein. Eight ewes received no further treatment. At surgery, 12 ewes were given 10 mg of progesterone (i.m.) along with an intravaginal pessary containing 30 mg flurogestone acetate and were either ovariectomized (n=5) or lutectomized (n=7). Five ewes were ovariectomized only. The second interval (Experiment 2, days 14 to 17) was chosen to study the maximal rises of PGF 2α associated with the completion of luteal regression and the preovulatory increase of oestrogen. Ewes were laparotomized and catheterized on day 14 and either received no further treatment (n=5), or were lutectomized (n=6), ovariectomized (n=5) or ovariectomized and implanted with oestradiol-17β (n=5). Five utero- ovarian venous samples were collected, every 30 min for 2 hours beginning at 0600 and 1800 on each day in each experiment, and assayed for PGF 2α . In a third experiment, 15 bred and 12 nonbred ewes were laparotomized and catheterized on day 12. One third of each type remained intact, while two thirds were ovariectomized and half of those received 10 mg of progesterone (s.c.) and an intravaginal sponge containing 30 mg of progesterone on day 12. Utero-ovarian samples were collected at 15-minute intervals for 3 hours on day 13. Neither the average day of occurrence of the first peak of PGF 2α (control, 12.1; lutectomy plus progesterone, 11.6; ovariectomy plus progesterone, 12.0; ovariectomy, 12.2) nor the mean number of peaks detected in each ewe during the sampling periods on days 10 to 14 (2.8, 3.7, 3.2 and 3.4, respectively) differed among groups in Experiment 1. The mean number of peaks of PGF 2α detected in each ewe during days 14 to 17 did not differ among groups in Experiment 2. Neither of the patterns of concentrations of PGF 2α studied (mean within sampling period over time and natural logarithm of the variance within sampling period over time) differed among groups in either experiment. Concentrations of PGF 2α increased after ovariectomy in Experiment 3 and were restored to values similar to intact ewes by replacement therapy with progesterone. These data do not support the idea that increases in oestrogen are involved in regulating patterns of uterine secretion of PGF 2α during the ovine oestrous cycle or the initiation of maternal recognition of pregnancy. In addition, progesterone may not be necessary after day 9 for initial rises of PGF 2α to occur on days 12 and 13, but does appear to be necessary to sustain normal patterns of secretion of PGF 2α beyond day 14.

Role of progesterone in regulating uteroovarian venous concentrations of PGF2 α and PGE2 during the estrous cycle and early pregnancy in ewes

The role of progesterone in regulation of uteroovarian venous concentrations of prostaglandins F2 alpha(PGF2 alpha) and E2 (PGE2) during days 13 to 16 of the ovine estrous cycle or early pregnancy was examined. At estrus, ewes were either mated to a fertile ram or unmated. On day 12 postestrus, ewes were laparotomized and a catheter was inserted into a uteroovarian vein. Six mated and 7 unmated ewes received no further treatment. Fifteen mated and 13 unmated ewes were ovariectomized on day 12 and of these, 7 mated and 5 unmated ewes were given 10 mg progesterone sc and an intravaginal pessary containing 30 mg of progesterone. Uteroovarian venous samples were collected every 15 min for 3 h on days 13 to 16 postestrus. Mating resulted in higher mean daily concentrations of PGE2 in the uteroovarian vein than in unmated ewes. Ovariectomy prevented the rise in PGE2 with day in mated ewes but had no effect in unmated ewes. Progesterone treatment restored PGE2 in ovariectomized, mated ewes with intact embryos. Mating had no effect on mean daily concentrations of PGE2 alpha or the patterns of the natural logarithm (1n) of the variance of PGF2 alpha. Ovariectomy resulted in higher mean concentrations and 1n variances of PGF2 alpha on day 13 and lower mean concentrations and 1n variances of PGF2 alpha on days 15 and 16. Replacement with progesterone prevented these changes in patterns of mean concentrations and 1n variances of PGF2 alpha following ovariectomy. It is concluded that progesterone regulates the release of PGF2 alpha from the uterus, maintaining high concentrations while also preventing the occurrence of the final peaks of PGF2 alpha which are seen with falling concentrations of progesterone. This occurs in both pregnant and non-pregnant ewes. Progesterone is also needed to maintain increasing concentrations of PGE2 in mated ewes.

Changes in porcine, ovine, bovine and equine blood progesterone concentrations between collection and centrifugation

Abstract The aim of this study was to determine if different methods of handling porcine, ovine, bovine and equine blood between collection and centrifugation influence measurable progesterone levels. A 2 × 2 × 5 factorial experiment was conducted for each species with heparin (with or without), temperature of incubation (4 and 22°C) and time of incubation (0, 6, 12, 24 and 48 h) as the main effects. Following centrifugation, plasma and serum samples were stored at −20°C until progesterone concentrations were determined by radioimmunoassay. Method of handling porcine and equine blood between collection and centrifugation did not affect the levels of progesterone. However, heparinized blood held at 4°C resulted in the most consistent levels of progesterone over time. Progesterone levels were fairly consistent across time in the ovine blood by all methods of handling except heparinized blood incubated at 22°C. By 24 h after collection, plasma progesterone concentrations decreased by 50% for the ovine blood incubated at 22°C with heparin. Decreases were detected by all the methods of handling the bovine blood between collection and centrifugation. The rate of decline, however, was considerably faster for blood held at 22°C than blood held at 4°C. At 12–48 h after collection, the concentrations of progesterone averaged only 5% of the time 0 sample for blood incubated at 22°C. In contrast, at least 30% of the progesterone values in the time 0 sample were detected between 12 and 48 h of incubation for the blood held at 4°C.

Effect of prostaglandin F2α (PGF2α) on sources of progesterone and pregnancy in intact, ovariectomized and hysterectomized 90–100 day pregnant ewes

Abstract A single dose of 8 or 16 mg of PGF 2 α per 58 kg body weight was injected intramuscular into intact, ovariectomized or hysterectomized 90–100 day pregnant sheep in three separate experiments. Both doses of PGF 2 α decreased the weights of the corpora lutea ( P ≤0.05) and the concentration of progesterone in ovarian venous plasma at 72 hr ( P ≤0.05) compared to the 0 hr sample within treatment groups and to control ewes at 72 hr in intact and hysterectomized pregnant ewes. In hysterectomized pregnant ewes, progesterone in jugular plasma declined ( P ≤0.05) from 0 to 72 hr but never fell below 4 mg/ml and this decrease in progesterone after 8 or 16 mg PGF 2 α was greater than in control hysterectomized ewes ( P ≤0.05). There was a significant decrease in progesterone over time in jugular or uterine venous plasma in the presence of absence of the ovaries in 90–100 day pregnant ewes ( P ≤0.05) but the profiles of progesterone were not different between vehicle and PGF 2 α -treated ewes ( P ≥0.05). Uterine venous progesterone never declined below 30 ng/ml in the presence or absence of the ovaries and there was a significant quadratic increase ( P ≤0.05) in uterine venous progesterone toward the end of the 72 hr sampling period indicating an increase in steroidogenic activity of the placenta. PGF 2 α did not affect the number of abortions in intact or ovariectomized pregnant ewes ( P >0.05). Thus, the corpus luteum of sheep at 90–100 days of pregnancy is functional and responsive to PGF 2 α , placentomes are functional but do not appear to be responsive to the doses of PGF 2 α tested and PGF 2 α was not an abortifacient over the 72 hr treatment period.

Effect of prostaglandin F2α on uterine or ovarian secretion of prostaglandins E and F2α in vivo in 90-100 day hysterectomized, intact or ovariectomized pregnant ewes

Abstract Vehicle or 8 or 16 mg of PGF2α per 58 kg body weight was given intramuscularly to intact, hysterectomized or ovariectomized 90–100 day pregnant ewes in three separate experiments. Both doses of PGF2α increased PGF2α in ovarian venous plasma compared with controls at 72 hr post treatment in intact (P≤0.05) but did not in hysterectomized (P≥0.05) 90–100 day pregnant ewes. Concentrations of PGE in ovarian venous blood of intact ewes did not differ (P≥0.05) between treatment groups and were equivalent to concentrations of PGE determined in uterine venous plasma. PGE was decreased in ovarian venous plasma by PGF2α in hysterectomized ewes (P≤0.07). PGE in uterine venous plasma averaged 6 ng/ml over the 72-hr treatment period in intact and ovariectomized 90–100 day pregnant ewes and was 12 fold greater (P≤0.05) than PGF2α which averaged 500 pg/ml in uterine venous plasma. Both PGF2α and PGE increased (P≤0.05) by 64 hr in uterine venous plasma of the 8 mg PGF2α — treated intact pregnant ewes. A significant quadratic increase (P≤0.05) was observed for PGF2α and PGE in the vehicle and both PGF2α treatment groups of intact ewes at the end of the 72-hr sampling period. It is concluded that the uterus and ovaries secrete significant quantities of PGE but little PGF2α during midgestation. In addition, PGF2α increased uterine secretion of PGE in vivo . PGE may be a placental stimulator of ovine placental secretion of progesterone or PGE may protect placental steroidogenesis from actions of PGF2α.

Effects of indomethacin, luteinizing hormone (LH), prostaglandin E2 (PGE2), trilostane, mifepristone, ethamoxytriphetol (MER-25) on secretion of prostaglandin E (PGE), prostaglandin F2α (PGF2α) and progesterone by ovine corpora lutea of pregnancy or the estrous cycle

Two experiments were conducted to determine the luteotropin of pregnancy in sheep and to examine autocrine and paracrine roles of progesterone and estradiol-17 beta on progesterone secretion by the ovine corpus luteum (CL). Secretion of progesterone per unit mass by day-8 or day-11 CL of the estrous cycle was similar to day-90 CL of pregnancy (P > or = 0.05). In experiment 1, secretion of progesterone in vitro by slices of CL from ewes on day-8 of the estrous cycle was increased (P < or = 0.05) by LH or PGE2. Secretion of progesterone in vitro by CL slices from day-90 pregnant ewes was not affected by LH (P > or = 0.05) while PGE2 increased (P < or = 0.05) secretion of progesterone. Day 8 ovine CL of the estrous cycle did not secrete (P > or = 0.05) detectable quantities of PGF2alpha or PGE while day-90 ovine CL of pregnancy secreted PGE (P < or = 0.05) but not PGF2alpha. Secretion of progesterone and PGE in vitro by day-90 CL of pregnancy was decreased (P < or = 0.05) by indomethacin. The addition of PGE2, but not LH, in combination with indomethacin overcame the decreases in progesterone by indomethacin (P < or = 0.05). In experiment 2, secretion of progesterone in vitro by day-11 CL of the estrous cycle was increased at 4-h (P < or = 0.05) in the absence of treatments. Both day-11 CL of the estrous cycle and day-90 CL of pregnancy secreted detectable quantities of PGE and PGF2alpha (P < or = 0.05). In experiment 1, PGF2alpha secretion by day-8 CL of the estrous cycle and day-90 ovine CL of pregnancy was undetectable, but was detectable in experiment 2 by day-90 CL. Day 90 ovine CL of pregnancy also secreted more PGE than day-11 CL of the estrous cycle (P < or = 0.05), whereas day-8 CL of the estrous cycle did not secrete detectable quantities of PGE (P > or = 0.05). Trilostane, mifepristone, or MER-25 did not affect secretion of progesterone, PGE, or PGF2alpha by day- 11 CL of the estrous cycle or day-90 CL of pregnancy (P > or = 0.05). It is concluded that PGE2, not LH, is the luteotropin at day-90 of pregnancy in sheep and that progesterone does not modify the response to luteotropins. Thus, we found no evidence for an autocrine or paracrine role for progesterone or estradiol-17 36 on luteal secretion of progesterone, PGE or PGF2alpha.

Effects of prostaglandin F2α (PGF2α) on secretion of estradiol-17β and cortisol in 90 to 100 day hysterectomized, intact and ovariectomized pregnant ewes

Abstract Vehicle or 8 or 16 mg PGF 2α /58 kg/body weight (BW) was given intramuscularly to intact, hysterectomized and ovariectomized 90 to 100 day pregnant ewes in three separate experiments. Hysterectomy alone decreased (P⩽0.05) estradiol-17β in jugular venous blood by 80 percent within 16 hours and profiles of estradiol-17β did not differ (P⩾0.05) among vehicle or 8 or 16 mg PGF 2α /58 kg/BW-treated ewes. Profiles of estradiol-17β differed (P⩽0.05) in intact pregnant ewes treated with 8 or 16 mg PGF 2α /58 kg/BW when compared to controls and in ovariectomized (P⩽0.10) 90 to 100 day pregnant ewes treated with 16 mg PGF 2α /58 kg/BW. Estradiol-17β decreased (P⩽0.05) over time in vehicle and 8 mg PGF 2α /58 kg/BW-treated intact and in vehicle-treated ovariectomized 90 to 100 day pregnant ewes. Cortisol decreased (P⩽0.05) over time in hysterectomized, intact, and ovariectomized 90 to 100 day pregnant ewes, but did not differ (P⩾0.05) among vehicle or 8 or 16 mg PGF 2α /58 kg/BW-treated ewes. It is suggested that estradiol-17β has a role in regulating ovine placental steroidogenesis.

Effects of prostaglandin F2α (PGF2α) on secretion of pregnancy specific protein B (PSPB) and placentome weights in intact or ovariectomized 90 to 100 day pregnant ewes

Abstract Vehicle or 8 or 16 mg PGF2α/58 kg/body weight (BW) was given intramuscularly to intact or ovariectomized 90 to 100 day pregnant ewes in two separate experiments. Treatment with 8 mg PGF2α in intact 90 to 100 day pregnant ewes increased (P≤0.05) placentome weights, but not in ovariectomized 90 to 100 day pregnant ewes (P≥0.05). Concentrations of PSPB in uterine venous plasma of control 90 to 100 day intact pregnant ewes over the 72 hour sampling period averaged (52±5 ng/ml). Profiles of PSPB in uterine plasma in the 16 mg PGF2α/58 kg/BW-treated ewes differed (P≤0.05) from control or 8 mg PGF2α-treated 90 to 100 day intact pregnant ewes. Pregnancy specific protein B was increased (P≤0.05) at 64 hr in intact 90 to 100 day pregnant ewes by treatment with 8 mg PGF2α/58 kg/BW. There was a quadratic increase (P≤0.09) in PSPB in uterine venous plasma of all three treatment groups of intact 90 to 100 day pregnant ewes. Concentrations of PSPB in uterine venous plasma of control 90 to 100 day ovariectomized pregnant ewes over the 72 hr treatment period averaged (90±5 ng/ml). Profiles of PSPB did not differ among the vehicle, 8 mg PGF2α or 16 mg PGF2α-treated ovariectomized 90 to 100 day pregnant ewes. There was a quadratic increase (P≤0.10) in PSPB in uterine venous plasma of ovariectomized 90 to 100 day pregnant ewes treated with 8 or 16 mg PGF2α/58 kg/BW. It is suggested that PSPB may have a role in regulating placental steroidogenesis.