Differences in synthesis and degradation of serum proteins in normal and hepatoma-bearing animals.

Rats bearing Morris liepatoma 7800 and Morris hepatoma 7777 have serum protein compositions which differ from normal rats. There is a slight decrease of albumin and an increase in a-globulin proteins in the circulating blood of the tumor-bearing animals. The increase in a-globulin is larger than would be expected if globulin would just compensate for the slight decrease in albumin, resulting in increased protein levels in the hepatoma-bearing animals. Synthesis of serum proteins released into the circulating blood was similar in host and normal rats. a-Globulin proteins in tumor-bearing rats had a decreased rate of breakdown, accounting for the absolute increase of these proteins. The capacity of liver tissue and hepatoma tissue to synthesize albumin differs 11-fold, with the hepatomas showing the lower rate of synthesis. In vitro determinations showed a 6to 7-fold difference. Host liver had the same synthetic capacity as normal liver. Both total protein synthesis and albumin synthesis are inhibited by cycloheximide and puromycin. The albumin synthesized by the hepatomas is apparently not released into the circulating blood to any great extent.