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Jian H. Song1 , Gary A. Rohrer1 , Thomas Wise1 *, J. Joe Ford1 *
U.S. Department of Agriculture, Agricultural Research Service, U.S. Meat Animal Research Center, Clay Center, Nebraska 68933-0166 1
The androgen receptor (AR) which is located on the X chromosome was chosen as a candidate gene that may regulate testicular development and sperm production in boars. Previous studies in this lab reported the AR cDNA coding sequence and its trinucleotide (CAG, CGG) repeat expansions in exon 1. Length of CAG and CGG repeat expansions was not variable in boars, but in humans these repeats are associated with testicular dysfunction. In the current study developmental changes in AR gene expression were evaluated for possible association with poor negative feedback control of luteinizing hormone in neonatal male pigs (Ford and Schanbacher, Endocrinology 100:1033, 1977). Hypothalami, pituitaries and testes were collected from fetuses (n=10, Day 105 of gestation) and boars at 10 days of age (n=9) and adulthood (n=6). AR mRNA was detected by reverse transcription and polymerase-chain reaction (RT-PCR), and its protein was localized by immunocytochemistry (ICC). Both RT-PCR and ICC indicated that neither AR transcripts nor protein were detected in the pituitary from fetuses and piglets at day 10 of age, whereas AR transcripts were observed at significantly greater (P>0.01) steady-state concentrations in pituitary from adult boars. AR transcripts were expressed in the testes of boars at all ages; however, AR protein was only observed in adult testes by ICC. Low levels of AR mRNA were also observed in hypothalamus tissue from the fetuses, piglets and adult boars. These results indicate that the basis for the dysfunctional negative feedback control of luteinizing hormone in neonatal male pigs is the absent or low concentration of AR in the pituitary gland.
This abstract is being presented on Tuesday, August 3 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.