Protein and RNA synthesis in pituitary tumors from F344 rats given implants of estrogen.

The synthesis of total proteins, growth hormone, and prolactin and the incorporation of radioactive precursors into RNA was studied in Pituitaries from normal F344 rats and rats given implants of 15 mg diethylstilbestrol (DES). Prolonged DES treatment (greater than 50 days) induced pituitary tumors in male and female rats. The tumor tissue had a high rate of cell protein synthesis and an unusual capacity to synthesize a single-protein hormone (prolactin). After 17 days of DES treatment, the increase in prolactin synthesis in the hyperplastic pituitaries was not as marked as that in the tumors. At the time of tumor induction and high prolactin synthesis, incorporation of uridine or cytidine into RNA was not stimulated, and orotic acid incorporation in tumors from male rats was decreased. During early estrogen treatment (5 and 17 days), significantly less uridine was incorporated into RNA. These data suggested that the increment in protein and hormone synthesis promoted by DES may be related to a decrease in RNA turnover.