Establishment and maintenance of pregnancy after embryo transfer in ovariectomized mares treated with progesterone

Pregnancy was established and maintained after embryo transfer in 3 ovariectomized mares treated with progesterone only. Four ovariectomized mares were used as recipients, and 7 transfers were performed. Progesterone in oil, 300 mg i.m. daily, was given starting 5 days before transfer of a 7-day embryo. If the mare was pregnant at 20 days, progesterone treatment was continued to 100 days of gestation. The 3 pregnant mares carried to term and delivered live foals with normal parturition, lactation and maternal behaviour. No differences were seen between pregnant and non-pregnant ovariectomized mares in jugular plasma concentrations of oestrogen, LH or FSH from day of transfer (Day 7) to Day 20. Pregnant ovariectomized mares showed a rise in LH, reflecting production of horse CG, starting at Day 36. Oestrogen values remained low until Day 50.     

Progesterone maintenance of the placental progesterone receptor and placental growth in ovariectomized rats

These studies examine the trophic effects of progesterone (P) on the progesterone receptor (Rp) and growth of the decidua basalis (DB) and junctional zone (JZ) in the rat placenta. Pregnant rats were ovariectomized (Ovx) in mid-pregnancy and received steroid replacement therapy consisting of implantation of P pellets (25 mg) and injections of estradiol (E), 2 micrograms s.c., daily. Placental protein synthesis, measured by 3H-leucine incorporation in vitro, decreased more than 99% within 24 h of Ovx. However, treatment with P immediately after castration maintained control levels of synthesis. Delay of P treatment for 4 h caused a 60% decline in protein production measured 20 h later (p less than 0.01). Intraperitoneal implantation of a 50-mg pellet of the antiprogestin, RU-38486, in intact pregnant rats decreased protein synthesis by 50% within 6 h and by more than 90% 12 h and 24 h post-implantation (p less than 0.01). Growth of DB and JZ in Ovx rats treated for 48 h with P and/or E was studied both histologically and by changes in protein and DNA content. Rp binding activity was also measured by exchange assay under equilibrium conditions. Only P was able to reverse the effects of Ovx on growth of the DB and JZ. P also maintained Rp levels in the DB above those observed in Ovx and Ovx + E-treated groups (p less than 0.01). The Rp may be a constitutive product in the JZ since binding activity was not altered by Ovx or by steroid treatments. This study shows that P is clearly a trophic hormone of the maternal and chorioallantoic placenta and is essential for placental growth, cellular differentiation, and histological integrity.     

Estradiol and progesterone differentially regulate formalin-induced nociception in ovariectomized female rats

Clinical and preclinical studies have found sex-specific differences in the discrimination and perception of inflammatory stimuli. The emerging picture suggests that the biological basis of these differences resides in the regulatory activity of gonadal hormones in the central nervous system. This study describes the effects of ovarian hormones in inflammatory pain processes. Ovariectomized rats received estradiol and/or progesterone, and the number of paw flinches was measured after 1, 2.5 or 5% formalin administration. Both estradiol and progesterone altered the number of flinches only after 1% formalin administration. Estradiol significantly reduced the overall number of flinches during Phase II of the formalin nociceptive response while progesterone attenuated Phase I of the response. After co-administration of estradiol and progesterone, progesterone reversed estradiol's analgesic effect in Phase II, however, estradiol did not reverse progesterone's analgesic activity in Phase I. To determine if estradiol effects are receptor-mediated, tamoxifen (selective estrogen receptor mediator, 15 mg/kg) or alpha-estradiol (an inactive isomer of estradiol, 20 microg) were utilized. Tamoxifen decreased the number of formalin-induced flinches during Phase II while alpha-estradiol did not affect any formalin-induced responses. When co-administered with estradiol, tamoxifen failed to reverse estradiol's effect, suggesting both tamoxifen and estradiol activate similar intracellular mechanisms. Although Western blot analysis detected the presence of estradiol alpha and beta and progesterone B receptors in the spinal cord, hormone replacement treatments had no effects on the levels of these receptors. We postulate that the mechanisms by which estradiol and progesterone induce analgesia occur through the activation of their receptor at the spinal cord level.     

The effect of progesterone on the activity-wheel running of ovariectomized rats

Progesterone treatment failed to significantly depress activity-wheel activity elicited by food deprivation in either ovariectomized or ovariectomized estrogen-treated rats. These results indicate: (1) that the lack of effect of progesterone on the activity of ovariectomized rats is not due only to their already low level of activity; and (2) that the depressant effect of progesterone on activity in the estrogen-treated ovariectomized rat is, to a large extent, a specific inhibition of estrogen facilitation of activity, rather than a nonspecific activity depressant effect.     

Effects of estrogen and progesterone on uterine sialic acid in ovariectomized rats

The effects of estradiol-17β and progesterone on uterine sialic acid of ovariectomized rats have been examined. In contrast to a previous report, progesterone was found in two of three experiments of different design to increase uterine sialic acid concentration above that produced by estradiol-17β alone; in the third experiment, it had no significant effect. This effect of progesterone was independent of the duration of treatment with exogenous hormones or of whether or not uterine luminal fluid was removed by blotting before assaying sialic acid. In a factorially designed experiment with four levels of estradiol-17β and three of progesterone, a dose-response relationship was found between estradiol-17β, but not progesterone, and uterine sialic acid concentration. It is concluded that, in some circumstances, estrogen and progesterone can act synergistically to increase uterine sialic acid concentration.     

The effect of estradiol and progesterone application on leptin concentration in ovariectomized rats

The aim of the present study was to investigate the effects of estradiol and progesterone application on leptin secretion in ovariectomised rats. The study included 30 adult female Sprague-Dawley rats. Rats were divided into three groups as follows: Group 1; Sham ovariectomy group (n=10), Group 2; Ovariectomy group (n=10), Group 3; Ovariectomized and estradiol propionate (450 microg/kg rat) and medroxyprogesterone acetate (15 mg/kg rat) supplemented group (n=10). One week after ovariectomy, rats in Group 3 were injected estradiol and progesterone for 4 weeks. Twenty-four hours after the last injection, rats were decapitated and blood samples were collected for leptin analysis. Serum leptin levels in Group 2 were found significantly higher than those in Groups 1 and 3 (p<0.01), while those in Group 3 were significantly lower when compared to Group 1 (p<0.0 1). The findings of the present study have shown that ovariectomy led to a significant increase in leptin levels. However, administration of estradiol and progesterone in combination following ovariectomy inhibites increases of leptin levels.     

Effect of eatradiol and progesterone on UDPgalactose pyrophosphatase activity in the endometrium of ovariectomized rats

Rat endometrium was found to contain a UDPgalactose pyrophosphatase for the hydrolysis of UDPgalactose into galactose 1-phosphate and UMP. The administration of 17β-estradiol to ovariectomized rats resulted in a significant decrease in the activity of the enzyme in endometrium while have little effect on that in myometrium. The response was linear with the dose of estradiol and as little as 0.07 μg per 100 g body weight produced maximum inhibition of the enzyme. Progesterone on its own had little effect on the enzyme activity but in combination with estradiol, it effectively prevented the inhibitory effect of estradiol. This inhibitory effect of estradiol on the activity of UDPgalactose pyrophosphatase may function in the regulation of glycoprotein biosynthesis in endometrium.     

Effect on pregnancy and plasma progesterone of exogenous steroid maintenance in ovariectomised pregnant rabbits

Pregnancy was maintained in ovariectomised does with 1 to 4 mg/day of exogenous progesterone with or without 0.2 μg/day of estradiol. Progesterone doses were designed to give similar plasma progesterone levels in treated groups to those found in normal pregnancy, and were measured and compared with normals since this comparison does not appear to have been published previously. In normal pregnancy mean progesterone levels reached 10 ng/ml on day 7 and then plateaued at 14 ng/ml between day 10 and 20 before falling to very low levels at parturition. In treated groups progesterone levels reached 10 ng/ml on day 6 and remained between 10 and 13 ng/ml until day 20 before declining. The difference between treated and control plasma progesterone plateau levels was tested using the t-test and was found not to be significant. The differences in progesterone levels between treated groups with or without estradiol, whether pregnant or not, were also not significant. Mean litter sizes (alive or dead) were not significantly different. However, fetal viability in the group maintained on progesterone alone was significantly lower than in the normal controls.     

Effects of 17 beta-estradiol and progesterone on intestinal digestive and absorptive functions in ovariectomized rats

The effects of low and high doses of 17 beta-estradiol and progesterone for 2 weeks on intestinal digestive and absorptive functions have been investigated in ovariectomized rats. The uptake of glucose was significantly enhanced following ovariectomy and administration of hormones restored the level of glucose uptake to that observed in sham-operated animals. Neither, the uptake of L-leucine nor calcium was affected after ovariectomy and treatment with the hormones. The activity of alkaline phosphatase (AP) of ileum was significantly elevated with the low and high doses of 17 beta-estradiol but in jejunum only at high doses. Progesterone alone did not alter AP activity but the combination of this hormone and 17 beta-estradiol significantly enhanced the jejunal and ileal AP activities. It seems that activity of AP is mainly under the control of 17 beta-estradiol. The activity of ileal disaccharidases and leucine aminopeptidase were enhanced at high doses of 17 beta-estradiol alone or in combination with progesterone whereas in the jejunum only AP activity was increased significantly. The present study indicates that 17 beta-estradiol plays an important role in regulating the activities of intestinal digestive enzymes and it is the ileal enzymes which are more prone to its action.