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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Publications at this Location » Publication #140299
Title: ENDOCRINE AND MOLECULAR INFLUENCES ON TESTICULAR DEVELOPMENT IN MEISHAN AND WHITE COMPOSITE BOARS

Author
item MCCOARD, SUSAN - FORMER ARS EMPLOYEE
item Wise, Thomas
item Ford, Johny

Submitted to: Journal of Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/30/2003
Publication Date: 9/20/2003
Citation: MCCOARD, S.A., WISE, T.H., FORD, J.J. 2003. ENDOCRINE AND MOLECULAR INFLUENCES ON TESTICULAR DEVELOPMENT IN MEISHAN AND WHITE COMPOSITE BOARS. JOURNAL OF ENDOCRINOLOGY. 178(3):405-416.

Interpretive Summary: Sperm production in boars is positively correlated with number of Sertoli cells that develop within the testes before the onset of puberty. In boars that subsequently develop small testes, proliferation of Sertoli cells ceases by eight weeks of age; whereas, in boars that develop large testes, proliferation of Sertoli cells continues for an additional 6-8 weeks. Previous studies determined that the signals for this continued proliferation occur before birth of boars. The objective of this study was to evaluate developmental changes in thyroid hormones and other key physiological markers produced by Sertoli cells, in relation to breed differences in proliferation and maturation of Sertoli cells in Meishan (MS) and White Composite (WC) boars. Plasma concentrations of triiodothyronine (T3) and free T3 were greater in MS compared to WC boars during fetal life. Thyroid hormone receptors (THR) within testes increased during fetal life in association with increased plasma concentrations of T3, indicative of increased thyroid responsiveness of the testis during this time. This study illustrates that transient neonatal hyperthyroidism in MS boars during late gestation is associated with subsequent decline in proliferation and early maturation of Sertoli cells. Therefore, these observations indicate a potential role for thyroid hormone in the modification of Sertoli cell development, thereby influencing growth and differentiation of the testis in pigs. These findings will impact the design of subsequent studies that address methods to improve sperm production in boars.

Technical Abstract: The aim of this study was to evaluate developmental changes in thyroid hormone and other key endocrine hormones/molecular markers produced by Sertoli cells, in relation to breed differences in proliferation and maturation of Sertoli cells in Meishan (MS) and White Composite (WC) boars. Blood samples and testes were collected on days 60, 75, 90 and 105 postcoitum (dpc) and 1, 7, 14 and 25 postpartum (dpp). Testes were immunostained for thyroid hormone receptor-beta1 (THRbeta1), GATA4, Mullerian-inhibiting substance (MIS), P450c17 and inhibin subunits (alpha, betaA, betaB), and protein levels determined by densitometry. Plasma concentrations of free T3 were greater in MS (hyperthyroid) compared to WC (hypothyroid) boars (P<0.01) during fetal life, but the reverse was evident postnatally. Elevated levels of free T3 during fetal life were associated with increased levels of THRbeta1, indicative of increased thyroid responsiveness of the testis during this time, contrasting observations during early postnatal life. Localization patterns of THRbeta1, MIS, GATA4 and the inhibin subunits were consistent with previous studies. MIS protein levels declined more rapidly (P<0.001) in MS compared to WC Sertoli cells postnatally, consistent with earlier maturation of Sertoli cells as indicated by our previous study. This study illustrates that transient neonatal hyperthyroidism in MS boars during late gestation is associated with subsequent decline in proliferation and early maturation of Sertoli cells, followed by early onset of puberty in this breed. Therefore, these observations indicate a potential role for thyroid hormone in the modification of Sertoli cell development, thereby influencing growth and differentiation of the testis in pigs.