Host and tumor responses to varying rates of nitrogen infusion in the tumor-bearing rat.

The influence of variations in nitrogen content of nutritional substrate available to the tumor-bearing (TB) host on tumor growth and host have not yet been completely defined. One hundred fifty-two growing Fischer 344 rats were either transplanted with a sarcoma (TB) or injected with saline (NTB, day 0), had aseptic placement of superior vena cava catheter (day 14), and were infused with total parenteral nutrition solutions (days 18-28). Isocaloric solutions (approximately 50 kcal/d) contained either 0%, 5%, 16%, 33%, 67%, 100%, 133%, or 167% of normal intake of an adequate amino acid mixture. Final tumor weight in the 5% group (23.4 +/- 3.0 g) was significantly less than tumor weights of all other groups (range: 33.3 +/- 3.3 to 42.6 +/- 11.3) (p less than 0.05). The carcasses of TB animals were slightly smaller than NTB animals but showed no major alterations in protein, fat, or water composition. This study suggests that the tumor can be starved selectively by strictly nutritional means with complex accompanying host carcass and organ changes.