Rapid plasma clearance of albumin-acrolein adduct in rats

Protein adducts are used as markers of chemical exposure. Determination of the clearance rate of these adducts from the blood circulation will provide the time frame for their measurement. Radioactive albumin was prepared biosynthetically by repeated intraperitoneal injections of L-[4,5-3H]lysine to a rat. After an affinity purification, an aliquot of this native [3H-lysine]albumin was adducted with 5 mM acrolein. Both the native albumin (A-treated group) and the albumin-acrolein adduct (AAA-treated group) were intravenously injected to separate groups of rats, and the clearance of radioactivity from the plasma was measured as a function of time. At the end of the experiment (33 h after the injection), radioactivity in the whole plasma, and in homogenates of liver, kidney and spleen and their trichloroacetic acid(TCA)-soluble and -insoluble fractions in both A- and AAA-treated groups, was measured. The results, at the initial 11 h after the injection, showed that the radioactivity was cleared from the circulating plasma more rapidly in the AAA-treated group (32% of the injected radioactivity remained) than the A-treated group (52%). At 33 h after the injection, 22% of the injected radioactivity remained in the plasma in the AAA-treated group as compared to 32% in the A-treated group. The whole homogenates of liver and kidney and their corresponding TCA-soluble fractions showed higher radioactivity in the AAA-treated group as compared to the A-treated group. However, the TCA-insoluble fractions from livers and kidneys of the AAA-treated group showed lower radioactivity as compared to the A-treated group. These results indicated that the albumin-acrolein adduct was removed more rapidly from the circulation than the native albumin, and degraded more rapidly by the liver and kidney. There was no preferential removal or degradation of the adducted albumin by the spleen.