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Biology of Reproduction, Vol 23, 558-563, Copyright © 1980 by Society for the Study of Reproduction

Role of the Uterus and the Conceptus in Regulating Luteal Lifespan in the Mouse

ELIZABETH S. CRITSER 1, J. J. RUTLEDGE 1, , and L. R. FRENCH 1

1 Department of Meat and Animal Science, University of Wisconsin, Madison, Wisconsin 53706


The effect of the uterus and the conceptus on the lifespan of corpora lutea in pregnant and pseudopregnant mice was examined in five experiments. In Experiment 1, mice hysterectomized prior to mating or on Day 7 of pseudopregnancy (presence of vaginal plug, Day 1) had longer (P<0.0l) interestrous intervals (IEls) than did intact pseudopregnant mice or mice hysterectomized on Day 9 of pseudopregnancy.

Experiment 2 examined the effect of hysterectomy on Day 5, 6, 7, 8, 9, or 10 postmating on the IEI of pregnant and pseudopregnant mice. The IEIs of pregnant mice were not different from those of pseudopregnant mice when hysterectomy was performed 5, 6, or 7 days postmating. However, pregnant mice hysterectomized on Day 8, 9, or 10 had longer IEIs than did pseudopregnant mice (interaction of pregnancy status and day, P<0.01). Furthermore, the difference between pregnant and pseudopregnant mice was greater on Day 10 than on Day 8 or 9 (P<0.05). Pregnant mice hysterectomized on Day 10 had a mean IEI (17.5 ± 0.5 days. x ± SEM) nearly as long as gestation. Pseudopregnant mice hysterectomized on Day 8, 9, or 10 had IEIs comparable to those of intact pseudopregnant mice, indicating that the uterus exerts a shortening effect on luteal lifespan by Day 8 of pseudopregnancy.

Removal of the conceptuses, but not the uterus, at Day 7, 8, 9, 10, 11, 12, or 14 of pregnancy (Experiment 3) gave mean IEIs similar to those observed after hysterectomy during pregnancy (Experiment 2). In Experiment 3, removal of conceptuses on Day 10 of pregnancy or later gave IEIs which were approximately as long as gestation and longer (P<0.01) than the IEIs observed when conceptuses were removed on Day 9 or earlier.

Plasma collected at Day 8, 10, or 12 of pregnancy (Experiment 4) and extracts of conceptuses collected at Day 8, 9, 10, 11, or 12 of pregnancy (Experiment 5) were injected into cycling virgin females for 8 consecutive days, beginning on the day of estrus. Injection of plasma collected at Day 10 (but not at Day 8 or 12) of pregnancy and extracts of conceptuses from Days 10 and 11 (but not Day 8 or 9) of pregnancy inhibited (P<0.01) the occurrence of vaginal estrus, stimulated (P<0.0l) mammary development, and elevated (P<0.01) plasma progesterone levels. Although extracts of Day 12 placenta did not inhibit the occurence of vaginal estrus or elevate plasma progesterone levels, there was some indication of mammary development.

The results of these experiments indicate that 1) there is a uterine luteolytic mechanism in the mouse; 2) by Day 8 of pregnancy, conceptuses extend luteal lifespan by inhibiting the uterine luteolytic mechanism; and 3) by Day 10 of pregnancy, conceptuses produce substances with mammotropic and luteotropic activity which cause an additional extension of luteal lifespan.

 Submitted on February 26, 1980
Accepted on July 9, 1980






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Copyright © 1980 by the Society for the Study of Reproduction.