Submitted to: Animal Reproduction Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2009
Publication Date: 6/1/2010
Publication URL: http://handle.nal.usda.gov/10113/41980
Citation: Ford, J.J., Rohrer, G.A., Nonneman, D.J., Lunstra, D.D., Wise, T.H. 2010. Association of Allelic Variants of Thyroid-Binding Globulin With Puberty in Boars and Responses to Hemicastration. Animal Reproduction Science. 119(3-4):228-234. Interpretive Summary: Puberty in males is difficult to assign an exact date. The two studies reported in this manuscript used diameter of the seminiferous tubules at the time of hemicastration and the responses to hemicastration that were expressed in the remaining testes to investigate one aspect of pubertal development in boars, terminal differentiation of Sertoli cells. Littermate boars that differed in two allelic variants of thyroid-binding globulin (TBG) provided a unique experimental model as previous studies predicted that boars with the C allelic variant underwent pubertal development sooner than boars with the A variant. These two studies provided conclusive evidence that in boars with the C variant of TBG seminiferous tubules expanded at a younger age than in boars with the A variant, indicative of terminal differentiation of Sertoli cells. Additionally, boars that were hemicastrated at 25 days of age had a compensatory increase in number of Sertoli cells within the remaining testis such that at 10 months of age this number was equivalent to the number of Sertoli cells observed in both testes of control boars. These findings provide new information to investigators seeking to understand pubertal development of boars. Additionally, these findings document that TBG or genes that reside near TBG on the X chromosome are involved in regulation of pubertal development of boars.
Technical Abstract: Hemicastration of males increases weight of remaining testis when conducted before terminal differentiation of Sertoli cells. The current studies re-examined responses to hemicastration in one-quarter Meishan crossbred boars that differed for 2 alleles of thyroid-binding globulin (TBG). In the first experiment, boars at 25 days of age with either allele did not differ in degree of testicular development; however, at 56 days, boars with the C allele had more advanced testicular development than littermates with the A allele as evidenced by significantly heavier testicular weight, and these testes had seminiferous tubules with larger diameter and greater weight. At 10 months of age, boars hemicastrated at 25 days had a similar number of Sertoli cells in their single testis compared with both testes of control boars. However, in boars hemicastrated at 56 days number of Sertoli cells was less than the total number of Sertoli cells in the bilaterally intact controls; this reduction was greater (P < 0.05) in boars with the C allele than in those with the A allele. The second experiment confirmed earlier (P < 0.05) pubertal development in boars with the C allele relative to littermates with the A allele based on tubular larger diameter and the greater proportion of tubules with a distinct lumen at 60 and 80 days of age. These studies establish that boars with the C allele for TBG attain puberty at a younger age than those with the A allele and that boars hemicastrated at 25 days of age compensated yielding a similar number of Sertoli cells as both testes of control boars.