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DNA Synthesis and DNA Polymerase Activity in Leydig Cells of Diethylstilbestrol-stimulated Mouse Testes¹

Eleanor Roosevelt Cancer Research Center, Department of Biochemistry [B. W., O. C. R., D. N. F., L. T. S.], and Division of Infectious Diseases, Department of Internal Medicine [S. L. S.], University of Utah College of Medicine, Salt Lake City, Utah 84132, and American Cancer Research Center, Denver, Colorado 80214 [R. A. H.]

Using a modification of the collagenase dispersion method of Dufau et al., we examined changes in DNA synthesis produced by estrogens in the interstitial cells of mice that develop malignant Leydig cell tumors after prolonged estrogen administration.

Previous work in cryptorchid mice indicated that during continuous estrogen administration [³H]thymidine incorporation into DNA rises to a maximum in 3 to 4 days and then falls to approximately base levels within 2 to 3 weeks. This was confirmed both in Leydig cell concentrates of estrogen-treated mice after either injection with [³H]thymidine or incubation with [³H]thymidine in vitro. This DNA synthesis was blocked by hydroxyurea.

DNA synthesis in cells of estrogen-treated BALB/c mice of the Huseby substrain, which have a high incidence of Leydig cell tumors, was 5 to 11 times that in untreated controls. Cells from estrogen-treated C3H/Bi mice, which have a low incidence of Leydig cell tumors, showed only a 2- to 3-fold increase.

In the Huseby substrain the rise of DNA synthesis to a peak and subsequent recession were paralleled by a rise and fall in DNA polymerase activity. DNA polymerase ß did not show this variation. In C3H/Bi mice, neither polymerase showed significant change. The evidence suggests that the early estrogen-stimulated DNA synthesis is probably replicative and is associated with increased DNA polymerase activity.

¹ Supported by USPHS Research Grants CA-10935 and CA-05191 from the National Cancer Institute.

² To whom request for reprints should be addressed.

³ Present address: Department of Biochemistry, Loma Linda University School of Medicine, Loma Linda, Calif. 92354.

⁴ Present address: Department of Oncology, Henry Ford Hospital, Detroit, Mich. 48202.

Received 2/22/77. Accepted 11/11/77.