PGF2α Secretion Research Articles

Prostaglandin Production and Ovulation during Exposure of Amphibian Ovarian Follicles to Gonadotropin or Phorbol Estr in Vitro

Experiments were carried out at different times of hibernation to ascertain whether prostaglandin is produced by Rana ovarian follicles during gonadotropin- or 12- O-tetradecanoylphorbol-13-acetate (TPA)-induced in vitro ovulation. Ovarian fragments were cultured in amphibian Ringer in the presence or absence of frog pituitary homogene (FPH, 0.05 gland/ml) or TPA (1 or 10 μ M). After various periods of culture, incidence of ovulation was determined and prostaglandia F 2α (PGF 2α) accumulated in culture medium was measured by radioimmunoassay. FPH and TPA increased PGF 2α levels in medium in a dose-dependent manner. The time course of PGF 2α secretion and ovulation by FPH or TPA treatment varied during the hibernation period. In early-hibernation, FPH stimulated neither PGF 2α secretion and ovulation, but both events took place several hours later than those observed in late-hibernation. Some fragments obtained in mid-hibernation and most obtained in late-hibernation spontaneously produced PGF 2α in vitro without FPH or TPA treatment and in some instance spontaneously ovulated. Furthermore, FPH or TPA increased PGF 2α levels further or accelerated the time course of secretion by such fragments. In late-hibernation, PGF 2α secretion induced with FPH or TPA increased simultaneously with or later than onset of ovulation. Exogenous cAMP (2.5 m M) or 1-(5-isoquinolinylsulfonyl)-2-methyliperazine 9H-7, 100 μ M), a PKC inactivator, markedly suppressed FPH- or TPA-stimulated PGF 2α secrettion and ovulation in mid-hibernation. Indomethacin (IM, 5 μg/ml) strongly suppressed TPA- or FPH-stimulated PGF 2α production by fragments but its effect on ovulation varied among animals and at different times. IM suppressed ovulation of some ovarian fragments obtained in mid-hibernation, but failed to suppress hormone-induced ovulation in late-hibernation. Cycloheximide (5 μg/ml) and actinomycin D (1 μg/ml) effectively suppressed FPH-stimulated PGF 2α production and ovulation, whereas actinomycin D reduced but failed to significantly suppress TPA-induced PGF 2α production in mid-hibernation. In general, effects of ovulation inhibitors exhibited strong seasonal variations and were less efficient as the breeding season approached. Taken together, the data suggest that elevated levels of PGF 2α are associated with spontaneous and hormone-induced ovulation, and PKC mediates gonadotropin induction of PGF 2α but not steroid synthesis in Rana ovaries.

Endocrine Changes after Mating in Pregnant and Non-Pregnant Llamas and Alpacas

Plasma concentrations of oestradiol-17 beta, progesterone, 15-keto-dihydro-PGF2 alpha and luteinizing hormone (LH) were monitored in llamas and alpacas after mating with an intact male. Concentrations of LH and PGF2 alpha metabolite were high immediately after copulation. Ovulation occurred in 92% of the animals. The first significant increases in progesterone were recorded on day 4 after mating. In non-pregnant animals the lifespan of the corpus luteum was estimated to be 8-9 days. Luteolysis occurred in association with the release of PGF2 alpha. In pregnant animals, a transient decrease in progesterone concentrations was observed between days 8 and 18 in both species. No significant changes in PGF2 alpha secretion were registered during this period. Oestradiol-17 beta concentrations were high on the day of mating, declined to low values on day 4, and started to increase again on day 8. Peak values after luteolysis in non-pregnant animals were significantly higher than those registered in pregnant ones. Furthermore, concentrations of oestradiol-17 beta were elevated for a longer period in non-pregnant than in pregnant animals. The results suggest that progesterone from the corpus luteum exerts a negative influence on follicular activity in pregnant animals by reducing oestradiol-17 beta secretion.

Effects of progesterone and estradiol on prostaglandin endoperoxide synthase in ovine endometrial tissue

In experiment 1, 20 ovariectomized ewes were used to determine how progesterone and estradiol interact to regulate endometrial concentration and activity of prostaglandin endoperoxide synthase (PGS). Ewes were randomly assigned to one of four treatment groups: (1) control ( n = 5); (2) estradiol ( n = 5); (3) progesterone ( n = 5); (4) progesterone and estradiol ( n = 5). Groups 3 and 4 received twice daily injections of progesterone for 15 days. The dose of progesterone was varied to simulate concentrations of progesterone observed in intact ewes during the estrous cycle. Estradiol was administered to groups 2 and 4 by subcutaneous silastic implants which maintained circulating concentrations of estradiol of approximately 3 pg ml −1. Ewes were slaughtered on day 16. A portion of uterine tissue was fixed and stained, immunohistochemically, for PGS. Treatment with progesterone induced an increase in epithelial cell height ( P < 0.01) and an increase in intensity of staining for PGS in epithelial cells ( P < 0.01). Explants of caruncular endometrial tissue were collected from each ewe and incubated in the presence or absence of arachidonic acid (20 μg ml −1) to quantify release of PGF 2α, in vitro. Release of PGF 2α in the presence of arachidonic acid was used as a functional assessment of PGS activity. Release was greater for tissue collected from groups treated with progesterone ( P < 0.01). Within progesterone treated groups, release was greater for tissue from ewes that also received estradiol ( P < 0.05). Release of PGF 2α was enhanced by the addition of arachidonic acid ( P < 0.01). Maximal release of PGF 2α in the presence of arachidonic acid was observed in tissue from ewes receiving progesterone and estradiol. In experiment 2, 19 ewes were randomly assigned to one of four treatment groups: (1) control ( n = 4); (2) estradiol ( n = 5); (3) progesterone ( n = 5); (4) progesterone and estradiol ( n = 5). Steroids were administered as in experiment 1 with minor modification in doses of progesterone. Uteri were collected on day 16. Explants of caruncular endometrial tissue were incubated in the presence of one of four treatments: (1) no additions; (2) arachidonic acid (20 μg ml −1); (3) oxytocin (10 −6 M); (4) arachidonic acid and oxytocin. The effects of ovarian steroids on release of PGF 2α from caruncular endometrial explants were similar to those described in experiment 1. Both arachidonic acid and oxytocin increased release of PGF 2α ( P < 0.01, P < 0.01, respectively). However, release of PGF 2α was not enhanced by arachidonic acid when administered in the presence of oxytocin. We conclude that the ability of ovarian steroids to regulate endometrial secretion of PGF 2α may be exerted, in part, through their ability to regulate the concentration and activity of PGS.

Prostaglandin F 2α, progesterone and oxytocin production by cultured bovine luteal cells treated with prostaglandin E 2 and pregnancy-specific protein B

The objectives of this experiment were to study the effects of pregnancy-specific protein B (PSPB) and prostaglandin E 2 (PGE 2) on bovine luteal cell progesterone (P4), prostaglandin F 2α (PGF 2α) and oxytocin production. Corpora lutea were collected during the mid- (days 10–12; n = 5) or late-luteal (days 17–18; n = 5) stages of the estrous cycle. Luteal cells were dispersed and accessory cells removed. Luteal cells (1.5 × 10 5) were incubated in a 3 × 3 factorial arrangement and treated with PSPB (0, 2.5, or 5.0 μg) and PGE 2 (0, 100, or 200 ng) in 500 μL of Ham's F-12 medium. All cells were incubated for 18 h before adding treatments. Samples were then collected at 6 h and 12 h. During the 18 h pretreatment period, P4, PGF 2α, and oxytocin production was similar between the prospective treatment groups. The PSPB failed to increase P4 production. The PGE 2 × time interaction showed that P4 increased in response to PGE 2 treatment at 6 h ( P < 0.001) and 12 h ( P < 0.03). Also, the stage × time interaction indicated that mid-stage cells produced more ( P < .001) P4 than late-stage cells during the pretreatment period at 6 h and 12 h. The PSPB did not alter PGF 2α production by mid-stage cells, but increased ( P < .05) PGF 2α by late-stage cells. Also, PGE 2 stimulated ( P < 0.001) PGF 2α secretion by both mid- and late-stage cells; luteal cells treated with 200 ng of PGE 2 produced more ( P < 0.001) PGF 2α than 100 ng of PGE 2. Oxytocin secretion was not changed by treatment with PGE 2 or PSPB. Oxytocin production was greater ( P < 0.001) by mid-stage than late-stage cells during the pretreatment period at 6 h and 12 h. Oxytocin production was similar between the 6h and 12 h culture times within stage of the cycle. These data indicate that PSPB does bot change bovine luteal cell P4 or oxytocin production, but elevates PGF 2α in late-stage cells. The PGF 2 increases both P4 and PGF 2α, but does not alter oxytocin production. Lastly, PSPB and PGE 2 do not interact to promote P4, PGF 2α, or oxytocin production by cultured bovine luteal cells.

Relationship between phosphoinositide hydrolysis and prostaglandin F 2α secretion in vitro from endometrium of cyclic pigs on day 15 postestrus

The mechanism for the luteolytic release of prostaglandin (PG)F 2α in swine is not known. This study examined the potential role of oxytocin (OT)-induced phosphoinositide (PI) hydrolysis in promoting PGF 2α secretion in vitro from the endometrium of cyclic gilts on Day 15 postestrus. In Experiment 1, endometrial PI hydrolysis was increased (P < 0.05) by 100 nM OT and was increased quadratically (P < 0.05) by LiCl, but was not affected by the LiCI × OT interaction (P > 0.30). PI hydrolysis was maximal at 50 mM LiCl and declined at 100 mM LiCl. In Experiment 2, endometrial PI hydrolysis and PGF 2α secretion were similarly increased (P < 0.01) by 0, 0.1, 1, 10, and 100 nM OT in a dose-dependent manner. In Experiment 3, the linear increase in PI hydrolysis occurring 0, 3, 5, 10, and 20 min after treatment was greater (P = 0.01) for tissue treated with 100 nM OT than for the tissue treated with 0 nM OT. The quadratic increase (P < 0.05) in PGF 2α secretion occurring 0, 3, 5, 10, and 20 min after treatment was greater (P < 0.05) for tissue treated with 100 nM OT than for the tissue treated with 0 nM OT. In Experiment 4, AIF 4 − (an activator of G P and phospholipase C) similarly increased (P < 0.01) PI hydrolysis and PGF 2α secretion. In Experiment 5, PI hydrolysis (P < 0.01) and PGFZ. secretion (P < 0.05) were increased by 100 nM OT but were not stimulated by cholera toxin (an activator of G s and adenylate cyclase). Cholera toxin also did not enhance PI hydrolysis and PGF 2α secretion in response to 0.1 or 100 nM OT. These results are consistent with the hypothesis that OT may induce PI hydrolysis to stimulate the endometrial secretion of PGF 2α during corpus luteum regression in swine.

Evaluation of biochemical and structural changes in individual porcine corpora lutea during prostaglandin F 2α-induced luteolysis with an in vivo implant system

To date, no in vitro system has been devised to allow the study of both the functional and the structural regression of luteal cells in response to prostaglandin (PG) F 2 α . This study describes the use of a novel intraluteal PGF 2α implant system that results in the death of individual corpora lutea (CL), while surrounding CL on the same ovary remain fully functional. By this technique, it was possible to study both the functional and the structural regression of individual CL in vivo, without the confounding effects resulting from the systemic injection of PGF 2α. Biochemical measurements of individual CL included progesterone concentration, protein kinase C activity, and diacylglycerol levels. Structural measurements included luteal weight and the protein:DNA ratio, which was used to estimate cell size. Further, the determination of large luteal cell size was accomplished directly via light microscopy. Nonpregnant gilts were injected with 5 mg of estradiol benzoate every 12 hr from 8:00 a.m. on Day 11 to 8:00 a.m. on Day 13 to prevent uterine PGF 2α secretion. At 7:00 a.m. on Day 13, CL on one ovary were selected at random to receive PGF 2α implants (n = 4) or implant material only (n = 4), whereas the remaining CL on that ovary served as unimplanted controls. The other ovary was removed at that point, and the CL on that ovary served as 0-hr controls. Gilts were relaparotomized at 3, 6, 12, and 24 hr after CL implantation, the PGF 2α-implanted ovary was removed, and individual CL were evaluated. PGF 2α implanted CL exhibited a decline (P < 0.05) in progesterone concentrations at 12 and 24 hr and a decline (P < 0.05) in weight at 24 hr when compared with control CL (implant-only, unimplanted, and 0-hr control CL). Furthermore, the protein:DNA ratio was reduced (P < 0.05) in the PGF 2α-treated CL at 12 and 24 hr. Moreover, this change in the protein:DNA ratio (cell size) was consistent with the reduced diameter (P < 0.05) of the large luteal cell in the PGF 2α-treated CL. Protein kinase C activity and diacylglycerol concentrations did not change (P > 0.10) and therefore appear to be unassociated with either functional or structural changes in the PGF 2α-treated CL. Contrary to in vitro culture studies, the results of our in vivo study demonstrate no clear role for protein kinase C in the PGF 2α-induced luteolytic process. In contrast, our study does temporally link a decline in luteal progesterone concentrations with a decrease in the size of large luteal cells.

Follicular development during early pregnancy and the estrous cycle of the sow

The objective of this study was to monitor and compare follicle populations and follicular development in pregnant and nonpregnant sows from Day 3 to Day 20 after breeding. Twenty-four sows were paired within parity on the day of artificial insemination and were randomly allocated within pair for insemination with either killed (n=12) or live spermatozoa (n=12). All the sows were artificially inseminated with the pooled ejaculate of the same boar. From Day 3 through Day 20 post estrus, ovarian follicles were scanned daily by ultrasonography. Ultrasound images were recorded on videotape and were retrospectively analyzed. Follicles were mapped to indentify the existence of follicular waves. The follicles were then classified as small (< 3 mm), medium (3–5 mm), or large (≥5 mm). Pregnancy diagnosis was performed on Day 21 by ultrasonography. Pregnant sows maintained a constant proportion of the follicle population in the small, medium and large follicle categories. However, in the nonpregnant sows, the proportion of follicles in the various size categories remained constant until Day 15. Thereafter, the proportion of small follicles decreased (P < 0.05) from Day 15 to 20, and the proportions of medium and large follicles increased (P < 0.05). The predictability of pregnancy status on Day 20 based on follicle populations in any of the 3 follicle categories was low. Moreover, there was no evidence of follicular waves during the estrous cycle or early pregnancy. In conclusion, the proportion of small follicles decreased while medium and large follicle increased from Day 15 through Day 20 of the estrous cycle, but not during a similar stage of pregnancy. This latter finding concurs with follicle recruitment from the pool of small follicles for ovulation following PGF2α secretion to induce luteolysis, which reduces progesterone concentrations and thereby allows for the stimulation of the pool of small follicles by gonadotropins.

Control of in vitro prostaglandin F 2α and E 2 synthesis by caruncular and allantochorionic tissues from cows that calved normally and those with retained fetal membranes

High concentrations of PGF 2α and PGE 2 are produced by the uterus during the early postpartum period in cows and may play an important role in both placental separation and uterine involution. In the present study, we have examined the hormonal and intracellular control mechanisms involved in PGF 2α and PGE 2 secretion by caruncular and allantochorionic tissue in vitro. Tissue explants, obtained about 6 hr postpartum from cows that delivered normally (NFM, n = 10) or cows with retained fetal membranes (RFM, n = 4), were incubated for 6 hr and PGF 2α and PGE 2 concentrations in the medium were determined by radioimmunoassay. Addition of oxytocin (100 μU/ml), platelet activating factor (PAF, 100 ng/ml) and epidermal growth factor (EGF, 100 ng/ml) had no effect on secretion of PGF 2α from the caruncle, but oxytocin and PAF did stimulate PGE 2. There was no difference between groups of cows. All three substances stimulated PGF 2α from the allantochorion of NFM, but not RFM, cows and stimulated PGE 2 secretion from the allantochorion of both groups of cows. Incubation of the tissues with cholera toxin (100 ng/ml), dibutyryl cyclic adenosine 3′,5′-monophosphate (dibutyryl cAMP, 1mM), calcium ionophore A23187 (5 μM) or phorbol ester 12-myristate-13 acetate (PMA, 100 nM) showed that PGF 2α secretion is essentially via the calcium-protein kinase C effector pathway. However, calcium-protein kinase C and cAMP second messenger systems appear to be involved in the secretion of PGE 2. Prostaglandin secretion was sensitive to cycloheximide in both caruncular and allantochorionic tissues, suggesting that protein synthesis may be involved. In conclusion, these data show that in vitro PGF 2α secretion can be modulated by the agonists used only in allantochorion and is essentially via the calcium-protein kinase C effector pathway. PGE 2 secretion can be modifified in both caruncular and allantochorion tissues and involves both inositol triphosphate-diacylglycerol and cAMP second messenger systems.

Does exogeneous progestogen alter the relationships among PGF 2α, 13,14-dihydro-15-keto-PGF 2α, progesterone, and estrogens in ovarian-intact ewes around the time of luteolysis?

The exact mechanisms controlling uterine secretion of PGF 2α are not known. An animal model in which progestogen concentrations are kept high and corpora lutea are allowed to regress should be useful for studying the effects of progestogen and estrogens on uterine secretion of PGF 2α. Thus, the primary objectives of this study with ovarian-intact ewes were to determine 1) the effect of 6 α-methyl-17 α-hydroxyprogesterone acetate (MPA) on luteal life span and changes in jugular and vena caval concentrations of PGF 2α, 13,14-dihydro-15-keto-PGF 2α (PGFM), progesterone, and estrogens around the time of luteolysis, and 2) the relationships among changes in those compounds. The results indicate that MPA 1) reduced (P < .05) vena caval and jugular PGF 2α and PGFM concentrations, 2) did not affect luteal life span or progesterone concentrations, 3) increased (P < .05) jugular concentrations of estrogens, and 4) prolonged (P < .05) the interestrous interval by 7 d. Stepwise regression procedures indicated that MPA disrupted a number of the relationships among PGF 2α, PGFM, progesterone, and estrogens in vena caval and jugular plasma. Ovarian-intact, MPA-treated ewes may be useful for determining the mechanisms involved in controlling uterine secretion of PGF 2α.

Effects of onapristone on uterine prostaglandin production and plasma progesterone concentrations in guinea-pigs during early and mid-pregnancy.

Onapristone (a progesterone receptor antagonist) administered to guinea-pigs on days 11-14 of pregnancy had no effect on uterine PGF2 alpha output and endometrial PGF2 alpha synthesizing capacity when measured on day 15. Peripheral plasma progesterone concentrations were still high on day 15, although the weight of the conceptuses was decreased by 50%. These findings indicate that the lack of increase in PGF2 alpha production by the uterus during early pregnancy is not due to an inhibitory action of progesterone on uterine PGF2 alpha synthesis and release. The output of PGF2 alpha from the guinea-pig uterus remained low during early pregnancy, showing that the uterus is not the source of increased PGF2 alpha secretion, as indicated previously by an increase in PGF2 alpha metabolite concentrations in the urine, after day 24 of pregnancy. Of the conceptual tissues examined, the fetal placenta had the highest PGF2 alpha synthesizing capacity, and it increased 2.3-fold between days 29 and 36 of pregnancy. The fetal placenta may therefore be the source of increased PGF2 alpha production during pregnancy. Onapristone administered to guinea-pigs on days 27 and 28 or on days 34 and 35 of pregnancy resulted in the guinea-pigs being in the early, middle or late stages of abortion when examined on days 29 or 36, respectively. Increased PG production, particularly of PGF2 alpha, by the uterus occurred in those guinea-pigs that were in the middle or late stages of abortion; uterine PG production in guinea-pigs that were in the early stages of abortion remained low.(ABSTRACT TRUNCATED AT 250 WORDS)

Secretion of PGF2α and oxytocin during hyperthermia in cyclic and pregnant heifers

The effects of acute heat stress (HS) and oxytocin (OT) injection on plasma concentrations of PGF2α and OT were examined in cyclic (C; n = 15) and pregnant (P; n = 11) dairy heifers. On Day 17 of synchronized estrous cycles, animals were randomly assigned to either thermoneutral (TN; 20°C, 20% RH) or HS (42°C, 60% RH) chambers. The jugular vein of each heifer was cannulated and blood samples collected hourly for 4 h, then every 15 min for an additional 3 h. Oxytocin (100 IU) was injected (IV) 5 h after the start of blood collection. Plasma samples were assayed subsequently for concentrations of 13,14-dihydro-15-keto PGF2α (PGFM) and OT. During the 7-h experiment, body temperature of HS heifers reached 41.2°C as compared to 38.5°C in control heifers. Plasma concentrations of PGFM increased (P<0.05) and peaked 30 min after OT injection in C (890 pg/ml) and P (540 pg/ml) heifers. In C heifers, heat stress failed to alter PGFM concentrations either before or after OT injection. In the P group, PGFM concentrations following OT injection tended to be higher in HS heifers were further TN heifers (peak values of 690 vs. 410 pg/ml). Pregnant TN and HS heifers were further classified as responders or non-responders to OT challenge according to a cutoff value for PGFM of 193 pg/ml (overall mean of C heifers minus 1 SD). Five of six HS and one of five TN pregnant heifers were classified as responders (P<0.06). Oxytocin concentrations in plasma prior to injection of exogenous OT were not affected by HS or pregnancy status. It is concluded that in C heifers, acute HS in vivo does not cause any further rise in PGF2α secretion. However, in P heifers, HS appears to antagonize suppressive effects of the embryo on uterine secretion of PGF2α, as indicated by the larger proportion of P heifers responding to OT challenge.

Activity of phospholipase C and release of prostaglandin F2 by endometrial tissue from ewes during the oestrous cycle and early pregnancy

Oxytocin appears to play an important role in regulating uterine secretion of prostaglandin F2 alpha (PGF2 alpha) in sheep. Changes in uterine secretion of PGF2 alpha throughout the oestrous cycle and early pregnancy may be due to changes in the intracellular regulatory pathways that control synthesis of PGF2 alpha in response to oxytocin. In this experiment, caruncular endometrial tissue was collected from ewes throughout the oestrous cycle and early pregnancy. Endometrial tissue was incubated in vitro to assess release of PGF2 alpha and activity of phospholipase C (PLC) in response to oxytocin. Release of PGF2 alpha in the presence of arachidonic acid was used to assess the activity of prostaglandin H2 endoperoxide synthase (PGS). In non-pregnant ewes, oxytocin stimulated release of PGF2 alpha from endometrial tissue collected on days 14 and 16, but not on days 4-7, 10 or 12 after oestrus. This coincided with times when oxytocin stimulated the activity of PLC. Release of PGF2 alpha was enhanced by the addition of arachidonic acid to tissues collected on days 12, 14 and 16 after oestrus. As with tissue from nonpregnant ewes, oxytocin could stimulate release of PGF2 alpha on days 14 and 16 of early pregnancy. Yet, oxytocin had no effect on activity of PLC in tissue from pregnant ewes. Release of PGF2 alpha in the presence of arachidonic acid by tissue from pregnant ewes was similar to that in nonpregnant ewes at comparable times after oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

PGF 2α, PGE 2, prosgesterone, and estradiol-17β, secretion by the corpus luteum of the oviparous lizard, Podarcis sicula sicula. In vitro studies

The release in vitro of prostaglandin F 2α (PGF 2α), prostaglandin E 2 (PGE 2), progesterone, androgens and estradiol-17β by the corpora lutea (CL) of the oviparous lizard, Podarcis s. sicula, was studied. In addition, the in vitro effects of PGF 2α and PGE 2 on sex steroid release by CL were evaluated. Corpora lutea were divided into four types, according to their different developmental stage: CL1 (unshelled eggs in the oviduct); CL2 (shelled eggs in the oviduct); CL3 (eggs laid 6 h previously); CL4 (eggs laid 48 h previously) and were placed into culture. PGF 2α secretion was highest in CL4 incubated samples and lowest in CL2 and PGE 2 was highest in CL1 and CL2. Progesterone secretion was highest in CL2 and lowest in CL4; androgens were not detectable and estradiol-17β secretion was highest in CL2. PGF 2α decreased progesterone secreted by CL1, CL2 and CL3, while it did not modify release of androgens and estradiol-17β. PGE 2 did not affect sex steroid release. These data suggest a role of PGF 2α in inducing luteolysis, while PGE 2 could be implied in the maintenance of CL. A role of progesterone during gestation of Podarcis s. sicula was also confirmed.

Cell-type specific responses in prostaglandin secretion by glandular and stromal cells from pig endometrium treated with catecholestrogens, methoxyestrogens and progesterone

The pig conceptus and endometrium possess the ability to convert estrogens into catecholestrogens and catecholestrogens into methoxyestrogens. Experiments were carried out to evaluate the effect of catecholestrogens, methoxyestrogens and progesterone on the secretion of prostaglandin (PG) E and F 2α by porcine endometrial glandular and stromal cells in vitro. Both 2-hydroxyestradiol (2-OH-E 2, 0–20μM) and 4-hydroxyestradiol (4-OH-E 2, 0–20 μM) increased ( P<.05) PGE and PGF 2α secretion by stromal cells in a dose response manner. Two-hydroxyestradiol tended ( P<.1) to decrease PGF 2α production by glandular cells. Two-methoxyestradiol (20 μM) suppressed ( P<.05) PGF 2α secretion by glandular and stromal cells. Four-methoxyestradiol (20 μM) stimulated ( P<.05) PGE production and PGE:PGF 2α ratio. Progesterone (.1 μM) suppressed ( P<.05) PG secretion in both cell types. We conclude that catecholestrogens, methoxyestrogens, and progesterone may participate in the establishment of pregnancy by modulating PG production in the endometrium.

Effect of constant infusion of oxytocin on luteal lifespan and oxytocin-induced release of prostaglandin F 2α in heifers

Two experiments were conducted to determine whether constant infusion of oxytocin would prolong the luteal phase and inhibit uterine prostaglandin F 2α (PGF 2α) secretion in heifers. In Experiment 1, twelve heifers, treated with saline (SAL) or oxytocin (OXY) via jugular cannulae infusions (INF) or osmotic minipumps (OMP), were allotted at estrus into four treatment groups (n = 3). Treatments were: SAL-INF, SAL-OMP, OXY-INF and OXY-OMP. Physiological saline or oxytocin was given from Days 10 to 23 (Day 0 = estrus) of the estrous cycle. Method of treatment (jugular cannula infusion or osmotic minipump) had no effect (P > 0.05) on estrous cycle length or pattern of secretion of progesterone; therefore, data were pooled. Estrous cycle lengths were extended (P < 0.01) for heifers which received oxytocin (25.3 ± 0.4 d) compared to saline (20.5 ± 0.4 d). Luteolysis did not occur in oxytocin-treated heifers until after treatment ceased. Experiment 2 was designed and conducted identically to Experiment 1 with the addition of a “challenge” injection of oxytocin (100 IU oxytocin, i.v.) given on Day 16 of the estrous cycle. Treatment of heifers with oxytocin extended (P < 0.05) estrous cycle length by an average of 3 d compared to heifers treated with saline. The “challenge” injection induced (P < 0.05) secretion of PGF 2α (as measured by the stable PGF 2α metabolite, 15-keto-13,14-dihydro-PGF 2α) in saline-treated but not oxytocin-treated heifers. In both Experiment 1 and 2, serum concentrations of FSH were elevated (P < 0.05) in oxytocin-treated heifers. No increase was observed for LH or prolactin. The rise in estradiol-17β at luteolysis was not affected (P > 0.10) by treatment. In summary, constant infusion of oxytocin extended luteal lifespan, prolonged secretion of progesterone, and inhibited oxytocin-induced secretion of PGF 2α. Constant infusion of oxytocin did not affect serum concentrations of estradiol-17β, LH or prolactin; however, serum concentrations of FSH were elevated during the oxytocin treatment period.

Inositol phosphate formation in uterine tissue from two species of reptiles is stimulated by arginine vasotocin and influenced by stage of reproduction

Phosphoinositide hydrolysis, resulting in inositol trisphosphate (IP 3) and diacylglycerol (DG) formation, has been implicated in oxytocin-stimulated pulsatile secretion of prostaglandin F 2α (PGF 2α) from uterine endometrium of sheep and other mammals. In reptiles, arginine vasotocin (AVT) stimulates uterine secretion of PGF 2α. These studies investigated the ability of AVT to stimulate incorporation of [ 3H]inositol into inositol mono-, bis-, and trisphosphates in two reptilian species. In Experiment 1, AVT stimulated ( P < 0.01) IP formation in uteri from late-gravid (150 to 291%) and postpartum (104 to 363%) Yarrow's spiny lizards ( Sceloporus jarrovi). Inositol phosphate formation, in response to AVT, was greater ( P < 0.01 for IP 3 and P < 0.05 for total IP) for gravid (stage 40 embryos) and postpartum (1–2 days) lizards near the time of parturition than for lizards at other stages (stage 38–39 embryos or 7 days postpartum). Inositol phosphate formation was greater ( P < 0.05) in uterine tissue from gravid than from postpartum lizards. In Experiment 2, basal IP formation and the response to AVT were the greatest ( P < 0.01) in endometrium from late-gravid American alligators ( Alligator mississippiensis). AVT stimulated ( P < 0.02) IP synthesis in uterine endometrium from vitellogenic (136 to 394%), early-gravid (7 to 270%), late-gravid (315 to 1002%), postpartum (86 to 313%), and nonreproductive (292 to 322%) alligators. Results indicate that (1) AVT stimulates IP formation in the uterus of reptiles; (2) uterine IP formation increases in late-gravid reptiles; and (3) increased responsiveness to AVT may occur at parturition or oviposition.

Prostaglandin E and F 2α secretion by glandular and stromal cellsof the pig endometrium in vitro: Effects of estradiol-17β, progesterone, and day of pregnancy

Prostaglandins (PGs) are believed to play important roles in the establishment of pregnancy. Glandular and stromal cells were isolated from pig endometrium on days 11 through 19 of pregnancy and cultured in the presence of estradiol-17β (E 2) and progesterone (P 4) to determine the effect of day pregnancy and steroids on the secretion of PGE and PGF 2α. Estradiol at concentrations between .01 and 1 μM did not affect PGE and PGF 2α secretion into the medium by glandular and stromal cells. Progesterone (.1 μM) suppressed (P < .001) PGE and PGF 2α production from both cell types. Glandular cell secreted more (P < .01) PGF 2α than PGE, whereas stromal cells collected on days 11, 12, 13, and 19 secreted more (P < .05) PGE than PGF 2α. Stromal cells isolated from tissues collected on day 13 of pregnancy produced PGs with higher (P < .01) PGE:PGF 2α ratio than those from tissues harvested on other days of pregnancy. Glandular cells isolated from tissues collected on days 13 and 19 and stromal cells isolated from tissue collected on day 13 of pregnancy secreted more (P < .05) PGE and PGF 2α than cells isolated on other days of pregnancy. We conclude that: 1) P 4 has a suppressing effect on PG secretion; 2) endometrial glandular and stromal cells each produce a unique profile of PGs; and 3) endometrial cells harvested on different days of pregnancy secrete different amounts of PGE and PGF 2α.

Human endometrial epithelial cells grown on collagen in serum-free medium. Estrogen responsiveness and morphology

The aim of the study was to explore the possibility of using human endometrial epithelial cells in serum-free culture as a sensitive assay for hormonal effects on the human endometrium. Glands were isolated following enzymatic digestion of the endometrial tissue and plated on a collagen matrix. The epithelial cells were grown in either medium containing serum or in supplemented serum-free medium. No morphologic difference was found between cells grown in these two media for up to 5 days, using either light or scanning electron microscopy. Secretion of prostaglandin F2 alpha (PGF2 alpha) in response to estradiol was not lower in serum-free medium than in medium containing serum for the first 2 days of culture, whereas secretion declined after prolonged incubation in the serum-free medium. This response to estradiol was clearly dose-dependent, and it was further enhanced by addition of arachidonic acid, the precursor for prostaglandin synthesis, to the medium. Co-culture of endometrial stromal cells did not influence the secretion of PGF2 alpha by epithelial cells. We conclude that the secretion of PGF2 alpha from primary cultures of human endometrial epithelial cells grown on collagen in serum-free medium can be used for a limited period as an assay of estrogenic effects on the human endometrium.

Effects of progestagen treatment on concentrations of prostaglandins and oxytocin in plasma from the posterior vena cava of post-partum beef cows

The role of PGF-2 alpha in determining the lifespan of corpora lutea in the post-partum beef cow was investigated. In control cows (N = 5) induced to ovulate at Day 28 to 36 post partum by injection of 1000 i.u. hCG, corpora lutea had an average lifespan of only 8 days. In cows pretreated with 6 mg implants of a progestagen (norgestomet, N = 4) for 9 days, with implant removal 2 days before injection of hCG, luteal lifespan averaged 17.5 days. Concentrations of PGF-2 alpha in 9 hourly samples of plasma collected from the posterior vena cava via indwelling catheters were higher on Days 4 through 9 after injection of hCG (P less than 0.05) in the cows with short-lived corpora lutea. Greater release of PGF-2 alpha could therefore be a major factor in premature luteal regression. Concentrations of PGFM and oxytocin did not differ between cows with corpora lutea of short or normal lifespan. In a second experiment, concentrations of PGF-2 alpha in plasma from the posterior vena cava were examined during treatment with norgestomet (N = 8) or in contemporary controls (N = 7). In progestagen-treated cows, PGF-2 alpha was higher than in control cows (P less than 0.05), beginning on Day 3 of treatment and peaking on Day 5. It is concluded that the post-partum uterus increases secretion of PGF-2 alpha very early after first exposure to endogenous or exogenous progestagen.

Evaluation of progesterone deficiency as a cause of fetal death in mares with experimentally induced endotoxemia

SUMMARY The role of decreased luteal activity in embryonic loss after induced endotoxemia was studied in mares 21 to 35 days pregnant. Fourteen pregnant mares were treated daily with 44 mg of altrenogest to compensate for the loss of endogenous progesterone secretion caused by prostaglandin F2α (pgf2α) synthesis and release following intravenous administration of Salmonella typhimurium endotoxin. Altrenogest was administered daily from the day of endotoxin injection until day 40 of gestation (group 1; n = 7), until day 70 (group 2; n = 5), or until day 50 (group 3; n = 2). In all mares, secretion of pgf2α, as determined by the plasma 15-keto-13,14-dihydro-pgf2α concentrations, followed a biphasic pattern, with an initial peak at 30 minutes followed by a second, larger peak at 105 minutes after endotoxin injection. Plasma progesterone concentrations decreased in all mares to values &lt; 1 ng/ml within 24 hours after endotoxin injection. In group 1, progesterone concentrations for all mares were &lt; 1 ng/ml until the final day of altrenogest treatment. In 6 of 7 mares in group 1, the fetuses died within 4 days after the end of treatment, with progesterone concentrations &lt; than 1 ng/ml at that time. In the mare that remained pregnant after the end of treatment, plasma progesterone concentration was 1.6 ng/ml on day 41 and increased to 4.4 ng/ml on day 44. In group 2, all mares remained pregnant, even though plasma progesterone concentrations were &lt; 1 ng/ml in 4 of 5 mares from the day after endotoxin injection until after the end of altrenogest treatment. One group-2 mare appeared to develop a secondary corpus luteum before day 70, with progesterone concentrations greater than 1 ng/ml from day 36 through day 70. Daily altrenogest administration consistently prevented pregnancy loss, which usually follows induced endotoxemia. Altrenogest administration offers a reliable and practical treatment for the prevention of fetal loss following endotoxemia in mares &lt; 2 months pregnant. One group-3 mare remained pregnant, and in the other mare, fetal death was diagnosed 8 days after endotoxin administration, although this mare was still being treated with altrenogest. In that case fetal death was believed to be unrelated to the treatment.