Increased degradation of albumin in cancer is not due to conformational or chemical modifications in the albumin molecule.

This study has evaluated whether increased albumin degradation in a tumor-bearing host is dependent on previously recognized chemical and environmental modifications in the albumin molecule as observed by others and ourselves. For the purpose, adult sarcoma-bearing mice with increased albumin degradation and electrophoretic heterogeneity were used and compared to freely fed (FF) or food restricted control animals. Food restricted control animals such as pair-fed (PF) and pair-weighed (PW) served to match the anorexia and malnutrition observed in tumor-bearing animals. The serum albumin concentration was decreased (P less than 0.05) in tumor-bearing animals (33 +/- 5 g/liter) compared to pair-fed (40 +/- 3), pair-weighed (41 +/- 4), and freely fed control mice (43 +/- 3). Isoelectric focusing of plasma between pH 3 and 10 and pH 4 and 6.5 confirmed a different isoelectric point for albumin in tumor-bearing animals compared to control animals. Albumin degradation was 33% higher in tumor-bearing mice compared to freely fed controls (P less than 0.01). Tumor-bearing animals had also significantly increased turnover of albumin compared to all control animals (0.13 +/- 0.022 mg/hr/g animal vs 0.05 +/- 0.008 mg/hr/g in PW; 0.08 +/- 0.009 in PF, and 0.09 +/- 0.007 in FF). The acidic fraction of albumin had a more rapid fractional turnover than the more basic components in both tumor-bearing and control animals. However, both the anodal and the cathodal albumin in tumor-bearing mice had a higher turnover compared with corresponding fractions of albumin from control animals.(ABSTRACT TRUNCATED AT 250 WORDS)