Hormonal regulation of deoxyribonucleic acid polymerase beta activity in rat testis.

The content of DNA polymerase beta in whole rat testes drastically decreased upon hypophysectomy: at 1 and 2 weeks, to 12.5% and 5% of the control testes of sham-operated rats, respectively. DNA polymerase beta activity per cell (per milligram DNA) also decreased to 14% of the control within 2 weeks after hypophysectomy. The DNA polymerase alpha in the testis also decreased, but the DNA polymerase gamma was relatively resistant to hypophysectomy. The testicular DNA polymerase beta from hypophysectomized rats sedimented at 4.5 S, whereas that from sham-operated controls sedimented at 3.3 S. The reduced level of testicular DNA polymerase beta and the change in molecular size induced by hypophysectomy were largely reversed by daily injections of LH and FSH. The reduced activity was also fully reversed by the injection of testosterone. These results suggest that the level of DNA polymerase beta in the rat testis depends largely on the level of testosterone produced by Leydig cells in the testis itself, but is also regulated by pituitary gonadotropins.