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Hormonal and Nutritional Influences on the Incorporation of Uracil into Liver and Tumor RNA in the Rat^*

A. Cantarow, T. L. Williams and K. E. Paschkis

( Departments of Biochemistry and Medicine, Jefferson Medical College, Philadelphia, Pennsylvania)

Studies were made on the incorporation of uracil into RNA in different tissues in rats subjected to procedures designed to alter protein metabolism and tissue growth. Starvation, hypophysectomy, growth hormone, and cortisone were employed for this purpose, in rats with and without transplanted tumors. After the administration of growth hormone, uracil incorporation into liver RNA increased in adult rats but decreased in young, intact, and hypophysectomized animals and also in the RNA of certain tumors. Cortisone, in a dosage that decreased this incorporation in "preneoplastic" liver, had no such effect on normal liver, regenerating liver, the tumors studied, or the livers of the tumor-bearing animals. Starvation resulted in increased incorporation into RNA of tumors and of normal and regenerating liver, but not into RNA of the livers of the tumor-bearing animals. In the presence of a mammotropic tumor, incorporation of uracil was depressed in tissues in which high values are obtained characteristically. Utilization of this auxiliary pathway of nucleic acid biosynthesis in the rat may be variably influenced in different cells by hormonal and nutritional factors. This may serve to reveal differences among tissues that may not be apparent otherwise.

^* Supported in part by a grant (C-1307) from the National Cancer Institute, National Institutes of Health, U.S. Public Health Service.

Deceased January 27, 1961.

Received 11/30/61.