Protein turnover in a study of host-tumor relationships.

Abstract

Control mice and mice bearing implants of mammary adenocarcinomas in varying stages of autonomy were given injections of glycine-2-C14. Groups of fed and fasted mice were sacrificed at intervals up to 4 days. The total radioactivity of liver and kidney was found to decrease, but that of the more malignant tumors increased in both fed and fasted animals. The first few transplant generations after primary tumors responded to fasting in a manner similar to liver and kidney. By the fifth transplant generation, the total radioactivity of the tumor showed an increase, although some protein turnover was evident. TA3 ascites cells were labeled in vivo with glycine-2-C14. The cells were drawn out, washed, and injected into normal mice. Injected mice were killed 24 and 48 hours later. The total radioactivity remaining in the ascites cells as well as that found in liver, kidney, spleen, urine, and respiratory CO2 was measured. Data from three experiments indicated that the TA3 tumor is a “nitrogen trap” in the relative sense only, that approximately 9 per cent of the radioactivity was lost from the tumor cells every 24 hours.