Influence of total nitrogen, asparagine, and glutamine on MCA tumor growth in the Fischer 344 rat.

Previous studies from this laboratory have demonstrated that growth of the methylcholanthrene (MCA) sarcoma is dependent on total nitrogen substrate availability in vivo and on the specific amino acids asparagine and glutamine in vitro. This experiment determines whether these two phenomena can be used to selectively depress tumor growth and maintain host carcass. Sixty-two rats were inoculated with sarcoma and were infused for 10 days with isocaloric (60 kcal/day) TPN solutions at 100%, 16%, 10%, and 5% of normal nitrogen levels, either with (W) or isonitrogenously without (WO) the amino acids asparagine, glutamine, aspartic acid, and glutamic acid. W solutions contained 33% of these amino acids. Mean weights of 100 W tumors were significantly greater (p = 0.002) than all other groups. Total body weights minus tumor weights were similar in W versus WO animals at each rate of nitrogen infusion. Mean venous plasma concentrations of asparagine, aspartic acid, glutamine, and glutamic acid were similar in all eight groups. These data indicate that the same degree of tumor depression produced by nitrogen deprivation can also be produced by removal of asparagine, glutamine, and their precursors from nutrient solutions without adverse effects on carcass mass. The mechanisms involved are not readily explained by analysis of venous plasma amino acid concentrations.