Prolonged Maintenance of the Corpus Luteum of the Ewe by Continuous Infusion of Luteinizing Hormone

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Abstract
Continuous intravenous infusion of purified ovine LH into intact normal ewes starting on day 10–12 after heat prolonged the life-span of corpora lutea (CL) to arbitrarily chosen times of 20, 25, or 30 days in 62% of the test animals. The weights and progesterone concentratlons of the maintained CL indicate that they were endocrinologically as active as corpora lutea from nontreated control ewes on days 9–13 of the estrous cycle. Infusion of LH was less effective in maintaining CL to day 20 when begun on days 13 and 14 after heat than when begun on day 12, and totally ineffective when initiated on day 15. Furthermore, CL were not maintained to day 25 if the infusions were discontinued on day 20, indicating that ovine corpora lutea require continuous support by luteotrophic substances. Since the reproductive and endocrine systems of the experimental ewes were intact and presumably functional, we conclude that the continual administration of a pituitary luteotrophin overcame the alleged luteolytic effect of the uterus of the normal ewe.

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