Inhibition of Prostaglandin F2 or LH Induced Luteolysis in the Pseudopregnant Rabbit by 17 -Estradiol

Summary. Previous studies have suggested that prostaglandin F-2\g=a\(PGF-2\g=a\)may have a role in luteolysis in rabbits. Rabbits (4\p=n-\6/group) were given a single injection of saline, or 100, 500 or 2500 \g=m\g PGF-2\g=a\ (i.m.) on Day 7, 9, 12 or 15 of pregnancy or pseudopregnancy. Daily blood samples were taken via the marginal ear vein before and for 3 days after the PGF-2\g=a\ injection. Concentrations of serum progesterone were determined by radioimmunoassay in pseudopregnant rabbits. There were no significant differences between PGF-2\g=a\-treated and control rabbits on Days 7 or 9. On Day 12 of pseudopregnancy, progesterone concentration was significantly (P < 0\m=.\05) lower in treated than in control rabbits, the effect being dose dependent. On Day 15 of pseudopregnancy, it was not possible to distinguish between controls and treated groups because luteolysis occurred in all rabbits.In contrast, on Days 7 and 9 of pregnancy, the concentration of progesterone in treated groups was lower than in the control groups (P < 0.05), the effect being dose dependent. This difference was maintained throughout the sampling period and resulted in termination of pregnancy. By Day 12 of pregnancy, the response to PGF-2\g=a\ was transient, with a significant decline in progesterone for only 2 days, followed by a return to control concentrations and normal delivery of litters. On Day 15 of pregnancy, no treatment with PGF-2\g=a\ significantly altered progesterone concentration. Our results indicate that (i) there is a change in responsiveness to PGF-2\g=a\ over time during pregnancy and pseudopregnancy and (ii) there are differences between pregnancy and pseudopregnancy in the pattern of responsiveness.

Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Change in responsiveness of rabbit corpus luteum to prostaglandin F-2 during pregnancy and pseudopregnancy

Marcinkiewicz¹,

Moy²,

Bahr³

1992

“…In the rabbit, luteolysis can also be obtained by exogenous PGF-2a injections (Gutknecht et al, 1972;Keyes & Bullock, 1974) and PGF concentrations in uterine tissue increase with luteal regression (Miller et al, 1983). Nevertheless, a role of ovarian PGF in luteolysis in the rabbit cannot be excluded (Schlegel et al, 1988).…”

Section: Discussionmentioning

confidence: 99%

Relative roles of oestradiol and of the uterus in the maintenance of the corpus luteum in the pseudopregnant brown hare (Lepus europaeus)

Caillol¹,

Martinet²,

Lacroix³

1989

by the large ovarian follicles is the main luteotrophic factor in the brown hare. In old hares, the large amount of interstitial tissue could secrete oestrogens, and thus maintain pseudopregnancy. On Day 7 of pseudopregnancy, the uterus secretes a luteotrophic substance acting either directly on the ovary, or via the pituitary, to maintain oestradiol secretion by the follicles. In long-term hysterectomized females, the CL would be able to develop independently of any trophic substance, but for a reduced duration.

“…In this species, PGF-2a treatment causes luteo¬ lysis (Gutknecht, Duncan & Wyngarden, 1972) and hysterectomy blocks the luteal regression which normally occurs at about Day 16 in pseudopregnant animals (Scott & Rennie, 1970). However, in the rabbit there is no local utero-ovarian relationship (Hunter & Casida, 1967) or apposition of the utero-ovarian vein and ovarian artery (Del Campo & Ginther, 1972), and the question therefore arises of how the uterine luteolytic factor is transported to the ovary.…”

Section: Introductionmentioning

confidence: 99%

CL regression in the pseudopregnant rabbit and the effects of treatment with prostaglandin F-2 and arachidonic acid

Carlson¹,

Gole²

1978

During pseudopregnancy in the rabbit, plasma progesterone levels in the posterior vena cava fell rapidly from maximal concentrations of 9.8 +/- 0.7 (s.e.m.) ng/ml on Day 13 of pseudopregnancy to 2.0 +/- 0.6 ng/ml on Day 15. There was no significant increase in PGF levels at this time, although administration of indomethacin to a similar group of does delayed functional regression for over 7 days. Subcutaneous injection of 1 mg PGF-2alpha or 35 mg arachidonic acid on Day 9 of pseudopregnancy resulted in loss of luteal function as plasma progesterone levels fell significantly from about 6 to less than 1 ng/ml within 24 h. These findings indicate that the uterine factor responsible for luteolysis in the pseudopregnant rabbit may not be released in the form of PGF-2alpha.