Effect of continuous intrauterine administration of prostaglandin E2 on life span of corpora lutea of nonpregnant ewes.

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 TM minipump (25 • 6.5 ram) containing PGE2 (delivery rate of 37.5 /ag/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 PGF2c~, PGE 2 (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=.I) to be longer (17.8 -+ .4 days) than each