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Differences in the reproductive endocrine status of ewes in the early post-partum period and during seasonal anoestrus



Differences in the reproductive endocrine status of ewes in the early post-partum period and during seasonal anoestrus



Journal of Reproduction and Fertility 70(2): 591-597



More (P < 0.05) post-partum acyclic ewes (8 of 9) showed evidence of pulsatile LH [luteinizing hormone] release than did seasonally anestrous ewes (2 of 8). Mean plasma prolactin concentrations were higher (P < 0.05) in the post-partum ewes than in the seasonally anestrous ewes. Hypothalamic and pituitary cytosol estrogen receptor number, median eminence GnRH [gonadotropin releasing hormone] content and pituitary LH, FSH and prolactin contents were similar in the 2 groups of ewes. The number of nuclear-bound estrogen receptors was greater (P < 0.01) in pituitaries from seasonally anestrous ewes than in pituitaries from post-partum ewes. The basis of acyclicity in seasonally anestrous ewes and in post-partum ewes is probably due to their inability to generate LH pulse frequencies similar to that in the follicular phase of the estrous cycle. The higher LH pulse frequency in post-partum ewes, compared to that in seasonally anestrous ewes, sugests that pregnancy may partly negate the reduction in LH secretion that is associated with photoperiod-induced acyclicity. The lower number of nuclear-bound estrogen receptors in post-partum ewes suggests that there may be lower plasma estrogen levels and less ovarian follicular growth than in nonsuckling anestrous ewes.

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Accession: 001182344

Download citation: RISBibTeXText

PMID: 6422034

DOI: 10.1530/jrf.0.0700591


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