Effect of Continuous Intrauterine Administration of Prostaglandin E2 on Life-Span Corpora Lutea of Nonpregnant Ewes

Publisher Website
Google Scholar
Abstract
The antiluteolytic effect of prostaglandin (PG) E2 was tested in two experiments. In experiment I, seven nonpregnant ewes that had ovulated bilaterally, were laparotomized on day-11 postestrus. Uterine horns were isolated by ligatures between the internal and external bifurcations and around blood vessels in the intercornual area. An Alzet™ minipump (25 × 6.5 mm) containing PGE2 (delivery rate of 37.5 μg/hr for 7 days) was inserted into the lumen of one uterine horn and a minipump containing vehicle was inserted into the lumen of the other horn. Minipumps were replaced on days−17 and−23 in ewes that had not returned to estrus. On day −17, uterine and ovarian venous blood was collected from each side and assayed for PGF2α, PGE2 (uterine vein) and progesterone (ovarian vein). Ewes that returned to estrus were necropsied and weights of corpora lutea (CL) obtained. Five ewes returned to estrus. Cycles in these ewes tended (P=.l) to be longer (17.8 ± .4 days) than each ewes' previous cycle (16.6 ± .2 days). In two ewes that did not return to estrus by day−23 and −30, weight of CL and ovarian venous progesterone indicated unilateral maintenance of CL ipsilateral to the PGE2-treated horn. PGF2α and PGE2 in venous plasma did not differ between uterine horns. A minipump containing PGE2 (delivery rate of 75 μg/hr) or vehicle was inserted into the uterine lumen ipsilateral to the CL on day-11 in 16 nonpregnant ewes that ovulated unilaterally in experiment II. Minipumps were replaced every 7 days until estrus or day−40. One ewe treated with PGE2 did not return to estrus by day−40. Treatment with PGE2 increased the variance (P<.05) but not the mean of the cycle lengths as compared with controls (18.3 ± .8 vs 17.2 ± .3 days) in ewes that returned to estrus. Prostaglandin E2 delayed the normal decline of progesterone at the end of the estrous cycle (P=.05) but did not affect the secretion of LH observed either wice daily or at 15-min intervals for 2 hr on day-13 postestrus. While PGE2 at the doses tested had a local antiluteolytic effect in some ewes, consistent lengthening of luteal life-span by more than 2 days was not obtained. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.