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Animal Reproduction Laboratory, Michigan State University,3 East Lansing 48823
Abstract
The peptide structure of two releasing hormones was recently announced; these moleclules were synthesized and synthetic gonadotropin releasing hormone (GnRH) and thyrotropin releasing hormone (TRH) were made available to allow beginning investigational efforts in farm animals. The results of these investigations are reviewed.
GnRH causes release of LH in sheep, cattle and pigs and the magnitude of the response is related to dose. The effect of GnRH appears to be directly on the pituitary since this decapeptide causes a dose related release of LH from steer pituitary in vitro. Variation in the LH response to GnRH under different physiological conditions may result from differences in the steroid hormone environment. At least estrogen has been implicated in the female; enhancing the LH response to GnRH. Possible mechanisms of estrogen action are considered. TRH causes release of prolactin in ewes, cows and bulls. In addition, serum growth hormone and thyroxine are increased in lactating cows after TRH administration. TRH can stimulate a modest, but significant increase in milk production in dairy cows. Potential applications of GnRH and TRH to problems of animal agriculture are discussed.
1 Michigan Agricultural Experiment Station Journal Article No. 6164. Invitational paper presented at the 64th Annual Meeting of American Society o( Animal Science, Blackburg, Virginia, 1972.
2 Supported in part by NIH Grants No. AM 15899 and HD 06720.
3 Department of Dairy Science.
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