Transferrin and albumin distribution and turnover in the rat

Abstract

The distribution and turnover of I131-labeled rat transferrin and Il25-labeled rat albumin were measured simultaneously in control rats and rats that had been treated by bleeding or by injections of iron dextran, packed erythrocytes, cobalt, phenylhydrazine, methyl-cellulose, turpentine, or colloidal thorium dioxide. The tissue distribution of the two labeled proteins was also determined 8-9 days after their injection. The increase in plasma transferrin concentration in the rats treated with cobalt, methylcellulose, turpentine, and thoro-trast was found to be due to increased transferrin synthesis, not to redistribution between intra- and extravascular spaces or to decreased catabolism. Relatively more transferrin than albumin was found in the bone marrow and livers in most of the treatment groups but in all cases except after treatment with thorium dioxide this excess was only a small fraction of the total plasma transferrin, and did not represent binding by cells of sufficient transferrin to significantly alter the plasma transferrin concentration. After treatment with thorium dioxide both I313 and I125 accumulated in large amounts in liver and spleen. Nearly all the radioactivity was protein bound and probably represents accumulation of transferrin and albumin in reticuloendothelial cells of these organs.