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

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Abstract
Summary. The activities of DNA polymerase α (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 β decreased by 43% at 5 days (P < 0·01) and by 47% at 7 days (P < 0·001). The activity of DNA polymerase γ also decreased by 46% at 3 days (P < 0·02) and by 78% at 7 days (P < 0·01) after surgery. The amount of mRNA for DNA polymerase β decreased in parallel with enzyme activity. Since the sensitivity to heat inactivation of testicular DNA polymerase β was exactly the same as that from liver, the decrease in DNA polymerase β 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 β and γ activities might be related to the deleterious effects of elevated temperature on spermatogenesis. Keywords: DNA polymerase α, β, γ; topoisomerase I; rat; cryptorchid testes