Changes of enzymes involved in DNA synthesis in the testes of cryptorchid rats.

The activities of DNA polymerase alpha (EC 2.7.7.7) and topoisomerase I did not fluctuate up to 7 days after surgery to induce cryptorchidism and showed no significant difference from those in control testes (sham-operated). In contrast, the activity of DNA polymerase beta decreased by 43% at 5 days (P less than 0.01) and by 47% at 7 days (P less than 0.001). The activity of DNA polymerase gamma also decreased by 46% at 3 days (P less than 0.02) and by 78% at 7 days (P less than 0.01) after surgery. The amount of mRNA for DNA polymerase beta decreased in parallel with enzyme activity. Since the sensitivity to heat inactivation of testicular DNA polymerase beta was exactly the same as that from liver, the decrease in DNA polymerase beta activity may be, at least in part, due to reduced biosynthesis of enzyme protein. The morphological changes in cryptorchid testes suggested that the decrease in DNA polymerase beta and gamma activities might be related to the deleterious effects of elevated temperature on spermatogenesis.