Peripheral plasma levels of E and F series prostaglandins during pseudopregnancy in the rat

Prostaglandin E2 levels in uterine tissues and its relationship with uterine and luteal progesterone during the estrous cycle in dairy cows

Endometrial tissue homogenates obtained at luteal and follicular stages of the estrous cycle were determined for prostaglandin E2 and progesterone contents by EIA and RIA, respectively. In Experiment 1, the concentrations and changes of PGE2 in uterine tissues collected by biopsy before slaughter and subsequent samples collected at 30, 60 and 90 min after slaughter were measured. No significant differences were observed in the concentration of PGE2 preslaughter or at 30 and 60 min post slaughter. However, there was a significant decrease (P<0.01) in PGE2 concentration 90 min post slaughter. In Experiment 2, the concentrations of PGE2 in the ipsilateral and contralateral horns in relation to corpus luteum function were compared. A significant (P<0.05) interaction was found between stages of estrous cycle (luteal vs follicular) based on CL progesterone content, and type of uterine horn (ipsilateral vs contralateral) on uterine PGE2 levels. The PGE2 concentration was significantly higher (P<0.01) at luteal phase than at follicular phase. During the luteal phase PGE2 concentrations in tissues of the uterine horn ipsilateral to the corpus luteum was significantly higher (P<0.01) than the contralateral horn. The PGE2 concentration was low and did not differ significantly between horns during follicular phase. A parallel increase (luteal: high) and decrease (follicular: low) in PGE2 and progesterone concentrations were observed. Correlations were observed for CL progesterone and uterine PGE2 concentrations as well as for PGE2 and progesterone concentrations in uterine tissues (r=0.70 and r=0.60, respectively). The results show that the increase in PGE2 concentrations in uterine tissues coincides with the high uterine progesterone concentrations during luteal phase.

Temporal relationship between progestin and luteinizing hormone concentrations in pseudopregnant rats treated with prostaglandin-F2 alpha

The temporal changes in progesterone (delta 4P), 20 alpha-dihydroprogesterone (20 alpha-DHP) and luteinizing hormone (LH) concentrations in pseudopregnant (PSP) rats after treatment with a single subcutaneous Silastic-PVP tube containing 600 micrograms PGF2 alpha were correlated. Progesterone levels fell and LH levels rose significantly 2h after initiation of treatment, while 20 alpha-DHP levels were found to increase significantly 12h after treatment. Since the changes in delta 4P and LH concentrations occurred concurrently, it seems that the increase in LH levels could have been due to a direct effect of PGF2 alpha on the ovary causing a reduction in delta 4P and thus a negative feedback effect on LH release. Alternatively, PGF2 alpha might exert a direct effect on LH secretion at the hypothalamic-pituitary level.

Prostaglandins F in uterine and ovarian compartments and in plasma from the uterine vein, ovarian artery and vein, and abdominal aorta of pseudopregnant rats with and without deciduomata

Prostaglandins F were measured in uterine and ovarian compartments and in uterine venous, ovarian arterial and venous and abdominal aorta plasma and the uptake of 3H-PGF2 alpha by ovarian compartments of 240 pseudopregnant rats with or without bilateral deciduomata in five experiments. Concentrations of PGF in deciduomal tissue, uterine venous plasma, ovarian arterial and venous plasma, corpora lutea, and remainder of the ovary and 3H-PGF2 alpha in the ovary were consistently as high or higher in pseudopregnant rats with deciduomata as in the endometrium, ovarian compartments, or samples of plasma from the same blood vessels of pseudopregnant rats without deciduomata. Levels of PGF were consistently 3 to 7 fold higher in uterine venous than in plasma from the abdominal aorta. It is concluded that extended luteal maintenance by deciduomal tissue is by some mechanism other than an inhibition of PGF synthesis by the uterus, transfer of PGF locally to the ovary, or uptake of PGF by the ovarian compartments.

Termination of pseudopregnancy in rats by silastic-PVP-PGF2 alpha tube

The efficacy of a one-end or both-end open Silastic-polyvinyl-pyrrolidone (Silastic-PVP) tube containing 600 microgram prostaglandin-F2 alpha (PGF2 alpha) and placed subcutaneously on day-6 of pseudopregnancy (PSP) in the induction of premature termination of PSP was compared. A both-end open Silastic-PVP-PGF2 alpha tube was more efficacious in inducing an early termination of PSP with a mean duration of 7.8 days. By contrast, PSP females receiving a one-end open Silastic-PVP-PGF2 alpha tube showed a mean duration of PSP of 9.9 days. The shortened duration of PSP in both these treatment groups was significantly different from the control value of 13.1 days. The significant drop in progesterone (delta 4P) but rise in 20 alpha-dihydroprogesterone (20 alpha-DHP) occurred 24 hr after treatment in PSP rats treated with both-end open Silastic-PVP-PGF2 alpha tube, whereas similar changes in delta 4P and 20 alpha-DHP took place 48-72 hr after the deposition of a one-end open Silastic-PVP PGF2 alpha tube. It is concluded than an initial larger amount of circulating PGF2 alpha is needed to induce an early premature termination of PSP. The exposure of corpus luteum to a more sustained but lower level of PGF2 alpha leads to a slower response.

RMI 12,936 and pseudopregnancy in rats

RMI 12,936, when injected subcutaneously at a dose of 2 mg, either on Day 6 of psuedopregnancy (PSP-6) or on PSP-6,7 and 8, shortened the duration of PSP from 12.3 +/- 0.3 (control) to 8.3 +/- 0.1 or 8.7 +/- 0.2 days, respectively. During PSP, plasma progesterone (delta 4P) levels in the peripheral plasma showed a trend of decrease by PSP-9 (52.0 +/- 4.6 on PSP-8 to 42.3 +/- 3.1 ng/ml on PSP-9). Administration of RMI 12,936 on PSP-6 resulted in a significant decrease in delta 4P and pregnenolone (delta 5P) within 24 hr after treatment but caused no apparent changes in 20 alpha-dihydroprogesterone (20 alpha-DHP) levels. However, a significant decrease of delta 4P/20 alpha DHP ratio was encountered 24 hr after RMI 12,936 treatment. The persistent occurrence of proestrous smear after PSP termination, but absence of estrous vaginal cytology, might be attributed to the slight estrogenicity of RMI 12,936. After the premature termination of pseudopregnancy induced by RMI 12,936, the female rats were sexually receptive for at least 3 weeks but failed to conceive, suggesting that this compound has a prolonged contraceptive effect.

Prostaglandins E and F in uterine venous plasma in relation to peripheral plasma levels of progesterone and 20alpha-hydroxyprogesterone in the rat throughout pregnancy and parturition

Prostaglandins E and F in uterine venous plasma and progesterone (P) and 20alpha-hydroxyprogesterone (20alpha-OH-P) in peripheral plasma were measured by radioimmunoassays throughout pregnancy and parturition in the rat. E Prostaglandins are low (approx. 2 ng/ml) and maintain a more or less constant level throughout most of the pregnancy except just before parturition when they rise to 3.8 ng/ml on day 20. F Prostaglandin levels are always higher than E prostaglandins and show distinct peaks around day 5 (5 ng/ml), day 11 (7 ng/ml), and before parturition (8.4 ng/ml). Progesterone levels are higher than 20alpha-OH-P levels throughout most of the pregnancy (day 6-20); however, during early pregnancy (day 1-5) and before parturition more 20alpha-OH-P than P is present in peripheral blood. The possible role of uterine venous prostaglandin levels in altering the 20alpha-OH-P/P ratio during pregnancy and parturition is discussed.

Production of prostaglandins by the pseudopregnant rat uterus, in vitro, and the effect of tamoxifen with the identification of 6-keto-prostaglandin F1alpha as a major product

1 Prostaglandin production by rat uterus homogenates has been studied, in vitro, on days 2 to 13 of pseudopregnancy. 2 The highest production of prostaglandins occurred on day 5. 3 The amounts of prostaglandins F and D formed were higher than the amounts of prostaglandin E on every day studied. 4 The ratios of prostglandins F and D to prostaglandin E produced steadily decreased up to day 6. It then increased with the highest values occurring between days 10 and 13, 5 Progesterone levels in peripheral plasma increased rapidly from days 2 to 5, remained high up to day 9, then steadily decreased between days 10 and 13. 6 The anti-oestrogenic drug, tamoxifen administered on day 2, significantly inhibited the increase of prostaglandin production which occurred on day 5. Prostaglandin E production was inhibited more than the production of prostaglandins F and D. 7 Analysis of the uterine extracts by gas chromatography and mass spectrometry showed prostaglandin F2alpha, F1alpha (in trace amounts), E2 and D2 to be present. 8 The major product detected was 6-keto-prostaglandin F1alpha. Its identification forms an addendum to the paper. 9 Also present as a major product was 6(9)-oxy-11,15-dihydroxyprosta-7,13-dienoic acid.