THE RENAL AND HEPATIC DISTRIBUTION OF BENCE-JONES PROTEINS DEPENDS ONGLYCOSYLATION - A SCINTIGRAPHIC STUDY IN RATS

The aim of the present study was to evaluate renal and liver distribut ion of two monoclonal immunoglobulin light chains. The chains were pur ified individually from the urine of patients with multiple myeloma an d characterized as lambda light chains with a molecular mass of 28 kDa . They were named BJg (high amount of galactose residues exposed) and BJs (sialic acid residues exposed) on the basis of carbohydrate conten t. A scintigraphic study was performed on male Wistar rats weighing 25 0 g for 60 min after iv administration of 1 mg of each protein (7.4 MB q), as the intact proteins and also after carbohydrate oxidation. Imag es were obtained with a Siemens gamma camera with a high-resolution co llimator and processed with a MicroDelta system. Hepatic and renal dis tribution were established and are reported as percent of injected dos e. Liver uptake of BJg was significantly higher than liver uptake of B Js (94.3 vs 81.4%) (P<0.05). This contributed to its greater removal f rom the intravascular compartment, and consequently lower kidney accum ulation of BJg in comparison to BJs (5.7 vs 18.6%) (P<0.05). After car bohydrate oxidation, there was a decrease in hepatic accumulation of b oth proteins and consequently a higher renal overload. The tissue dist ribution of periodate-treated BJg was similar to that of native BJs: 8 2.7 vs 81.4% in the liver and 17.3 vs 18.6% in the kidneys. These obse rvations indicate the important role of sugar residues of Bence Jones proteins for their recognition by specific membrane receptors, which l eads to differential tissue accumulation and possible toxicity.