Evaluation of serum proteins in relation to body nitrogen in tumor-bearing rats

Assessment of visceral and somatic protein stores by serum proteins in surgical oncology patients has been difficult to interpret. Tumor-bearing (methylcholanthrene sarcoma) (TB) and nontumor-bearing (NTB) Fischer 344 rats were infused with a total parenteral nutrition solution at either 25, 100, or 175% of an infusion rate that provided sufficient nutrients for normal rat growth: On the fifth day after diet initiation, the rats were exsanguinated, decapitated, eviscerated, and skinned. Serum was analyzed for transferrin (TF), complement C3, albumin (ALB), retinol-binding protein (RBP), and transthyretin (TTR). Carcass (CAR) and organ (VIS) nitrogens were determined by the Kjeldahl method. TTR, TF, and RBP correlated significantly with TB and NTB VIS nitrogen and TB CAR nitrogen. The correlation of NTB VIS nitrogen with TTR, TF, and RBP (r range = 0.70-0.85, P less than 0.001) was higher than for TB rats (r range = 0.53-0.57, P less than 0.005). The correlation of TB carcass nitrogen (r range = 0.47-0.51, P less than 0.01) with TTR, TF, and RBP was higher than for NTB carcass nitrogen which was not significant (r range = 0.25-0.37, P less than 0.57). These data indicate that TTR, TF, and RBP do correlate with components of body nitrogen mass, but factors other than nutrition may influence their metabolism in the TB host.