Date of this Version
The thymus gland has been analyzed in depth in relation to its immunological function, but new evidence is accumulating that the thymus and its endocrine secretions (interferons, interleukins, thymic peptides) may be required for normal reproduction. The thymus gland regresses at puberty and pregnancy, indicative of the effect of gonadal steroids on the gland. Steroidal interactions have been hypothesized to mediate the secretion of some thymic peptides. Thymosin β4, a thymic peptide, seems to have an integrative role in gonadal function by promoting the release of gonadotrophin releasing hormone whereas thymosin α1 causes the release of adrenocorticotrophin releasing factor and stimulation of the adrenal gland. Evidence from rodents has established a strong role for the thymus and its secretions in reproduction, but thymic-gonadal relationships are unknown in farm species. The puberal period of development when the thymus regresses and ovarian function is initiated and the estrual period when there are maximum changes in ovarian hormones were utilized as models to monitor for relationships of thymic secretory peptides and reproductive function. The objectives of this study were to identify changes in thymic secretory peptides thymosin α1and β4 during the prepuberal period of development and during the estrous period.