Glucose metabolism and the percentage of glucose derived from alanine: response to exogenous glucose infusion in tumor-bearing and non-tumor-bearing rats.

Glucose and alanine metabolism were investigated in non-tumor-bearing (NTB) and tumor-bearing (TB) male F344 rats after a 24-hr fast and during the infusion of either 0.9% NaCl solution or glucose at 0.67 or 2.35 mg per 100 g total body weight per min. During 0.9% NaCl solution infusion, the plasma glucose level was higher (98.2 +/- 4.0 versus 85.8 +/- 8.1 mg per di; p less than 0.05), the whole-blood lactate level was lower (5.8 +/- 0.8 versus 8.3 +/- 1.6 mg per di; p less than 0.05), the glucose turnover rate was lower (0.72 +/- 0.04 versus 0.88 +/- 0.13 mg per 100 g total body weight per min; p less than 0.05), alanine turnover rate and the percentage of glucose derived from alanine was measured by [14C]alanine in the NTB and compared to the TB animals. In response to glucose infusions, the whole-blood lactate level rose in both groups but remained lower (7.1 +/- 0.9 versus 10.5 +/- 2.4 mg per dl at 0.67 mg per 100 g total body weight per min, p less than 0.05; 9.1 +/- 1.1 versus 19.3 +/- 5.5 mg per dl at 2.35 mg per 100 g total body weight per min, p less than 0.05; NTB versus TB) in the NTB than in the TB animals. The endogenous production rate of glucose as measured by [3H]glucose displayed a similar response to exogenous substrate in the NTB and TB animals but required a higher plasma glucose concentration to effect a similar degree of suppression in the TB group. The alanine turnover rate rose to a similar level, and the percentage of glucose derived from alanine was similarly depressed in the NTB and TB animals at each glucose infusion rate.