Conservation of nucleic acids by Ehrlich ascites-tumor cells II. Conservation of ribonucleic acid purines

Ehrlich mouse ascites-tumor cells have been labelled in vivo by the intraperitoneal injection of [8-14C]adenine. 1 to 2 days after labelling the cells are transplanted into new host animals. The radioactivity of the RNA-purines of the transplanted cells is completely retained over a period of 9-days growth. Determination of the radioactivity of the separated purines of RNA shows that from the 3rd to the 9th day of growth there is no change in the ratio of either specific or total activities of the RNA-purines. The total radioactivity contained in the acid-soluble purine nucleotides during this period is of the order of 1% of the radioactivity in the RNA. Between day 0 and day 3 of growth there is a consistent fall in the ratio of specific activities of RNA-purines which is not found after a second transplantation of labelled cells. If cells are allowed to remain in animals into which the labelled precursor has been injected there is a steady decline in the ratio of specific activities which ceases when the cells are transferred into hosts which have received no isotope. These findings suggest that: i, the RNA which is labelled on day 3 is stable; ii, there is some fraction of RNA still labelled 2 days after exposure to the precursor which is depleted of label within 3 days after transplantation; iii, there is a measurable effect of contribution of purine precursors by the host to the nucleic acids of the tumor.