ALUMINUM UPTAKE AND TOXICITY IN CULTURED MOUSE HEPATOCYTES

Hepatic aluminum (Al) accumulation in association with hepatobiliary dysfunction has been described in children receiving contaminated parenteral alimentation solutions and in aluminum-overloaded experimental animals. The mechanisms of hepatic Al uptake are not clearly understood, and it is not known whether Al is directly toxic to the hepatic cell or if toxicity occurs from the effect of Al on hepatic iron (Fe) metabolism. Al causes a microcytic hypochromic anemia and concomitant hepatic Al and Fe can accumulate in dialysis patients, suggesting that Al may alter Fe metabolism. Therefore, Al uptake and toxicity were studied in mouse hepatocytes in culture. Al accumulation, cell growth, media hepatic enzyme concentrations, and cell malonyldialdehyde concentrations, a marker of membrane lipid peroxidation, were measured in mouse hepatocytes grown in media containing either Al citrate, transferrin-Al (Tf-Al), or no additions over 96 h. Al uptake occurred only in cells grown in Tf-Al and Al citrate at 24 h and increased linearly achieving cellular concentrations at 96 h of 522 +/- 36 and 186 +/- 12-mu-g/L, respectively, compared with 31 +/- 3-mu-g/L (P < 0.001) in control media. Inhibition of cell growth occurred at 48, 72, and 96 h (P < 0.001), and media lactate dehydrogenase and aspartate aminotransferase concentrations increased starting at 48 and 72 h, respectively (P < 0.001), only in media containing Tf-Al. Cell malonyldialdehyde levels were significantly higher in Tf-Al-loaded mouse hepatocytes compared with control cells at 96 h (P < 0.05). Fe and Tf uptake were increased in Tf-Al-loaded compared with control cells (P < 0.001) at 24, 48, 72, and 96 h. The increased Fe uptake resulted from increased Tf receptor expression because Tf cell cycling time was not altered. These data indicate that Al uptake by mouse hepatocytes was predominantly through Tf, although nonspecific uptake of Al also occurred. Al toxicity was dependent on the intracellular Al concentrations achieved because toxicity was only observed in cells grown in media containing Tf-Al and not Al citrate. Al induced membrane lipid peroxidation either by a direct effect on the cell membrane or by increasing the uptake of Fe.