title: 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.
abstract: 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 age). 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 4 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 ng/ml at day 0 to 0.403 ng/ml at day 120; P less than 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 less than 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.
authors: U.S. Department of Agriculture, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, Nebraska 68933-0166.
authors: T
authors: T
authors: Wise
authors: M L
authors: ML
authors: Day
authors: D D
authors: DD
authors: Vakharia
mesh_terms: D000818:Animals; D002417:Cattle; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood*; D010052:Ovariectomy; D010053:Ovary / Q000502:physiology; D012741:Sexual Maturation / Q000502:physiology*; D000077596:Thymalfasin; D013947:Thymosin / Q000031:analogs & derivatives* / Q000097:blood; D000099201:Thymosin beta(4)
chemical_list: D004958:Estradiol; D007986:Luteinizing Hormone; D000077596:Thymalfasin; D013947:Thymosin; D000099201:Thymosin beta(4)