C.W. Weems

Effect of luteinizing hormone (LH), PGE2, 8-EPI-PGE1, 8-EPI-PGE2, trichosanthin, and pregnancy specific protein B (PSPB) on secretion of progesterone in vitro by corpora lutea (CL) from nonpregnant and pregnant cows.

Secretion of progesterone by Day 14 bovine corpora lutea (CL) of the estrous cycle and Day 200 CL of pregnancy was evaluated in vitro to determine what regulates secretion of progesterone by CL of pregnancy. Weights of Day 200 CL of pregnancy (4356 +/- 223 g) were heavier when compared to Day 14 CL of the estrous cycle of Brahman cows (3643 +/- 128 g; p < or = 0.05); however, both Day 14 and Day 200 minced CL slices secreted similar basal amounts of progesterone per unit mass (p > or = 0.05). Secretion of progesterone in vitro by Day 14 CL of the estrous cycle was increased at 4 and 8 h (p < or = 0.05) by 10 or 100 ng/mL luteinizing hormone (LH) and did not differ between doses (p > or = 0.05). Progesterone secretion in vitro by Day 200 CL of pregnancy was not increased (p > or = 0.05) by LH at 4 or 8 h. However, progesterone secretion in vitro by Day 14 CL of the estrous cycle or Day 200 CL of pregnancy was increased (p < or = 0.05) at 4 h by 10 or 100 ng/mL PGE2, which did not differ by dose or reproductive status (p > or = 0.05). At 8 h, Day 14 CL of the estrous cycle secretion of progesterone in vitro was increased (p < or = 0.05) by both doses of PGE2 but only at 8 h by 100 ng/mL from Day 200 CL of pregnancy (p < or = 0.05). Secretion of progesterone in vitro was not affected (p > or = 0.05) by 10 or 100 ng/mL 8-Epi-PGE1 or 8-Epi-PGE2 at 4 or 8 h from Day 14 CL of the estrous cycle or Day 200 of pregnancy. Trichosanthin increased (p < or = 0.05) secretion of progesterone in vitro by 10 ng/mL at 4 h and at 8 h by Day 14 CL of the estrous cycle or at 8 h by Day 200 CL of pregnancy but trichosanthin at 100 ng/mL did not affect (p > or = 0.05) secretion of progesterone in vitro by Day 14 CL of the estrous cycle or Day 200 CL of pregnancy at 4 or 8 h. Pregnancy specific protein B (PSPB) increased (p < or = 0.05) secretion of progesterone in vitro at 4 and 8 h by Day 14 CL of the estrous cycle and did not differ between incubation times (p > or = 0.05). PSPB increased secretion of progesterone at 4 h but not at 8 h (p > or = 0.05) by Day 200 CL of pregnancy. These data suggest that PGE2 or PSPB but not LH, 8-Epi-PGE1 or 8-Epi-PGE2 regulates luteal secretion of progesterone by bovine CL at mid-pregnancy. In addition, it is suggested that weights of bovine CL of pregnancy increase to compensate for a lack of placental secretion of progesterone.

Effects of Luteinizing Hormone (LH), PGE2, 8-Epi-PGE1, 8-Epi-PGF2α, Trichosanthin and Pregnancy Specific Protein B (PSPB) on Secretion of Prostaglandin (PG) E (PGE) or F2α (PGF2α) In Vitro by Corpora Lutea (CL) From Nonpregnant and Pregnant Cows

Abstract Both Day 14 corpora lutea (CL) of the estrous cycle and Day 200 CL of pregnancy secrete detectable prostaglandin E (PGE) and prostaglandin F 2 α (PGF 2 α) in vitro . Corpora lutea from Day 200 pregnant cows secrete more PGE and PGFα in vitro than Day 14 CL of the estrous cycle when incubated in control medium without treatments ( p ≤ 0.05). In addition, secretion of both PGE and PGF 2 α in vitro by both Day 200 CL of pregnancy and Day 14 of the estrous cycle increase ( p ≤ 0.05) with time in culture in the absence of treatments. The PGE: PGF 2 α ratio secreted at 4 h in the absence of treatments by Day 14 CL of the estrous cycle was 1.2 and at 8 h was 1.0 and did not differ ( p ≥ 0.05), while the PGE: PGF 2 α ratio secreted by 200 day CL of pregnancy in the absence of treatments at 4 h was 0.8 and at 8 h decreased ( p ≤ 0.05) to 0.4. The PGE: PGF 2 α ratio at 8 h by 200 day CL of pregnancy was lower ( p ≤ 0.05) than in the Day 14 CL of the estrous cycle at 4 or 8 h. Secretion of PGE or PGF 2 α was affected by luteinizing hormone, PGE 2 , 8-Epi-PGE 1 , 8-Epi-PGE 2 , trichosanthin, and pregnancy specific protein B (PSPB) and was time and dose dependent ( p ≤ 0.05). In summary, the altered ratio of PGE: PGF 2 α may explain the decreased secretion of progesterone at 8 h by Day 200 CL of pregnancy reported previously from the same samples. In addition, caution should be exercised in interpretation of progesterone secretion data with bovine CL studies in vitro . Also, PSPB may play an indirect role through PGE to regulate bovine luteal secretion of progesterone.

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.

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 luteinizing hormone (LH), pregnancy specific protein B (PSPB), or arachidonic acid (AA) on ovine endometrium of the estrous cycle or placental secretion of prostaglandins E2 (PGE2) and F2α (PGF2α) and progesterone in vitro

The objective of this experiment was to determine the effect of AA, LH, or PSPB on secretion of PGE2, PGF2alpha, or progesterone by ovine caruncular endometrium of the estrous cycle or placental tissue of pregnancy in vitro. Ovine caruncular endometrium of the estrous cycle (days 8, 11, 13, and 15) or caruncular/placental tissue on days 8, 11, 13, 15, 20, 30, 40, 50, 60, and 90 postbreeding were incubated in vitro with vehicle, AA, LH, or PSPB in M-199 for 4 and 8 h. Secretion of PGF2alpha by caruncular endometrium of non-bred ewes on days 13 and 15 and by caruncular/placental tissue of bred ewes on days 13, 15, 20, 30, and 40 was increased (P < or = 0.05) when incubated with vehicle and declined (P < or = 0.05) after day-40 in bred ewes. Secretion of PGF2alpha by day-15 caruncular endometrium of non-bred ewes and bred ewes was increased (P < or = 0.05) by AA on days 13 and 15 and by LH on day-15. Secretion of PGF2alpha by caruncular/placental tissue from bred ewes was (P < or = 0.05) by AA on days 13, 15, 20, 30, and 40 and by LH on days 15, 20, 30, and 40, after which the response decreased (P < or = 0.05). Secretion of PGF2alpha by caruncular endometrium of non-bred ewes during the estrous cycle or by caruncular/placental tissue of bred ewes during the first trimester was not affected by PSPB (P > or = 0.05). Secretion of PGE2 by caruncular endometrium of non-bred ewes did not change (P > or = 0.05) and was increased (P < or = 0.05) by caruncular/placental tissue on days 13-90 from bred ewes when incubated with vehicle. Secretion of PGE2 by endometrium from non-bred ewes was not affected (P > or = 0.05) by AA, LH, or PSPB, but was increased (P < or = 0.05) by AA or LH on days 13-50 and by PSPB on days 60 and 90 when incubated with caruncular/placental tissue from bred ewes. Secretion of progesterone by placental tissue of bred ewes increased (P < or = 0.05) on day-50 and continued to increase through day-90. In summary, uterine/placental tissue secretion of PGF2alpha is not reduced until the end of the first trimester of pregnancy in ewes. In addition, LH appears to play a role in luteolysis of non-bred ewes by stimulating caruncular endometrial secretion of PGF2alpha and on day-5 postbreeding to prevent luteolysis during early pregnancy by stimulating caruncular/placental secretion of PGE2 throughout the first trimester of pregnancy in sheep. Secretion of PGE2 by caruncular/placental tissue after day-50 of pregnancy appears to be regulated by PSPB, not LH.

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.

PGE2 induces its own secretion in vitro by bovine 270-day placenta but not by 200-day placenta.

Two separate experiments were conducted to determine whether prostaglandin (PG) E2 stimulates the secretion of progesterone by 270- or 200-day Brahman placentas in vitro. Secretion of progesterone, PGF2alpha, pregnancy specific protein B, or estradiol-17beta by 270-day Brahman placentas was not affected (p > or = 0.05) by PGE2, during the 4-h incubation period at the doses tested. Indomethacin or meclofenamic acid decreased (p < or = 0.05) 270-day Brahman placental secretion of PGE and PGF2alpha by 98 and 60%, respectively. However, PGE2 induced (p < or = 0.05) its own secretion, but not the secretion of PGF2alpha (p > or = 0.05), by 270-day Brahman placentas, even in the presence of indomethacin or meclofenamic acid at a dose of 100 ng/mL. Also, secretion of 8-Epi-PGE2 by Day 270 Brahman placentas was increased (p < or = 0.05) by PGE2. Secretion of progesterone, estradiol-17beta, or pregnancy specific protein B by 200-day Brahman placentas was not affected by PGE2, 8-Epi-PGE2, PGF2alpha, estradiol-17beta, or trichosanthin during the 4- or 8-h incubation period (p > or = 0.05). Secretion of estradiol-17beta at 8 h was lower (p < or = 0.05) in all treatment groups and did not differ (p > or = 0.05) among the 8-h incubation treatment groups. Secretion of PGE by 200-day Brahman placentas was reduced (p < 0.05) by indomethacin 72 and 82% and by meclofenamic acid 72 and 96%, respectively, at 4 and 8 h when compared to controls. Secretion of PGF2alpha was reduced (p < or = 0.05) 71 and 86% by indomethacin or 89 and 89% by meclofenamic acid at 4 and 8 h, respectively, and did not differ (p > or = 0.05) between 4 and 8 h of incubation. PGE2 did not (p > or = 0.05) induce secretion of PGE above what was added in any treatment group. PGE in culture media was increased (p < or = 0.05) by 8-Epi-PGE2, pregnancy specific protein B, and the 100 ng/mL PGF2alpha dose (p < or = 0.05), but not by PGE2, progesterone, estradiol-17beta, 8-Epi-PGF2alpha, or trichosanthin. Secretion of PGF2alpha by 200-day Brahman placentas was not affected (p > or = 0.05) by 8-Epi-PGE2, progesterone, or estradiol-17beta, but PGF2alpha secretion was increased (p < or = 0.05) by trichosanthin or PGE2, even in the presence of indomethacin or meclofenamic acid. It is concluded that PGE does not affect secretion of progesterone by 200- or 270-day bovine placentas, but, pregnancy specific protein B may regulate placental secretion of PGE. Also, indomethacin and meclofenamic may affect enzymes converting PGH to PGE rather than acting only on cyclooxygenase because indomethacin and meclofenamic acid lowered PGE secretion by 270-day Brahman placentas more than they lowered PGF2alpha. In addition, it is concluded that PGE2 can induce bovine placental secretion of PGE, but this is dependent upon the stage of gestation.

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.