INHIBITORY EFFECT OF TUMOR-BEARING BLOOD ON THE INCORPORATION OF LABELED LEUCINE INTO TISSUE PROTEINS

Abstract

About 25ml of blood from tumor-bearing rats, which had been transplanted with Walker carcinosarcoma 13 to 18 days before sacrifice, or of normal blood was infused into the juglar vein of normal rats, while removing the same volume of blood from the carotid artey. The incorporation into protein of L-leucine[U-¹⁴C], injected intraperitoneally 1hr after blood exchange, was inhibited with tumor-bearing blood; 73% in plasma, about 40% in liver, kidney, and spleen, 33% in bone marrow, and not significantly in pancreas, small intestine, and skeletal muscle, and the inhibition was reversed gradually and completely 17hr after blood exchange. In the incorporation of L-leucine[4, 5-³H] into protein of liver slices from rats which had been subjected to blood exchange 17hr before sacrifice, no difference was observed between tumorbearing and normal blood, while the isotope incorporation into protein was stimulated in liver slices of tumor-bearing rats as compared with that of normal rats, suggesting that such an inhibitory factor(s) may be inactivated in normal rats and that the synthesis of liver protein is stimulated in response to its continuous existence. The inhibitory effect on the isotope incorporation into plasma proteins was obtained with the cellular fraction but not with the plasma fraction of tumor-bearing blood.