Isoelectric points of urinary light chains in myelomatosis: analysis in relation to nephrotoxicity.

Measurements of the isoelectric point (pI), sialic acid content, and polymerisation were made of 43 light chains isolated from the urine of patients with myelomatosis excreting large amounts of light chains. The pIs ranged from 3.5-9.5, and 23 were greater than 7.0. Sialylation was detected in 62% of light chains, and 69% showed microheterogeneity of charge. There was no clear association between the pI, sialylation, or polymerisation and the presence of renal failure, as assessed by serum creatinine concentrations. Light chains with pI spectrotype in the basic range, however, were found to produce more proximal tubular dysfunction than acidic light chains.