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Effect of Albumin Fraction from Blood of Tumor-bearing Rats on Serum Protein Production by Isolated Perfused Normal Rat Livers¹

Department of Biochemistry, Thomas Jefferson University, Jefferson Medical College, Philadelphia, Pennsylvania 19107

It was previously postulated that whole blood from Walker 256 tumor-bearing rats carries a signal factor(s) which decreases the serum protein-synthetic activity of perfused normal rat livers. Preliminary isolated perfused normal rat liver experiments with albumin and -, ß-, and -globulin fractions, separated from blood of tumor-bearing rats on DEAE-Sephadex A-50 columns, indicated signal factor activity in the albumin fractions only. Further experiments were performed with albumin fractions obtained from large pools of blood from normal and tumor-bearing rats. Serum protein production was followed by: (a) determination of the incorporation of L-lysine-6-¹⁴C into total serum protein, which was precipitated with trichloroacetic acid; (b) oxidation of the dried protein to ¹⁴CO₂ by the Schöniger method; (c) absorption of the ¹⁴CO₂ in an ethanolamine-ethylene glycol monomethyl ether solution; (d) liquid scintillation counting.

From the results obtained, it is concluded that the signal factor activity in whole blood from Walker tumor-bearing rats is located in the broad albumin fraction of such blood, as fractionated on DEAE-Sephadex A-50. On the basis of the method of preparation, it is speculated that the signal factor substance(s) is a large molecule, possibly protein, or a smaller molecule tightly bound by a nondialyzable molecule. The addition of albumin fractions from normal blood to the perfusion media, whole blood or synthetic substitutes, had no significant effect on the protein-synthetic activity of the perfused rat liver under the conditions used.

¹ This work was supported in part by National Science Foundation Grants GB-12436 and GB-23914 from the Physiological Processes Section.

Received 3/ 2/71. Accepted 8/12/71.