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Endocrine relationships of thymosin alpha 1 thymosin beta 4 and luteinizing hormone throughout the prepubertal period of development in heifers ovariectomized heifers and ovariectomized heifers with estradiol implants






Journal of Reproductive Immunology 18(3): 225-236

Endocrine relationships of thymosin alpha 1 thymosin beta 4 and luteinizing hormone throughout the prepubertal period of development in heifers ovariectomized heifers and ovariectomized heifers with estradiol implants

To monitor the relationships of luteinizing hormone (LH) and thymosin-.alpha.1 and-.beta.4 in conjunction with possible gonadal feedback mechanisms that could alter thymic function (thymosin secretion), circulating thymosin-.alpha.1 and -.beta.4 and LH concentrations of control heifers (n = 6), ovariectomized heifers (n = 5) and ovariectomized heifers implanted with estradiol (n = 5) were determined during the prepubertal period (initiated at 266 days of ate0. Sequential blood samples were collected at 12-min intervals for 8 h before ovariectomy on day 0 and on days 8, 36, 50, 64, 78, 92, 106, 120 and 134 of the experiment. Thymosin-.beta.4 concentrations were not different between treatments. Thymosin-.beta. concentrations gradually decreased until day 92 of the study, then increased two-fold by day 134 of experimental sampling (400 days of age) when all control animals had attained puberty. Concentrations of thymosin-.alpha.1 changed little as animals matured, but peak amplitude did increase over time (0.287 nmg/ml at day 0 to 0.403 ng/ml at day 120; P < 0.05). Mean concentration, number of episodic peaks and peak amplitude of thymosin-.alpha.1 was increased in ovariectomized heifers in comparison to ovariectomized plus estradiol implants (P < 0.05). Prior to cyclic ovarian function (prepuberty), changes in circulating thymosin-.beta.4 concentrations seem to be independent of effects of gonadal steroids but thymosin-.alpha.1 was responsive to estradiol.


Accession: 007299172

PMID: 2266539



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