Light chain polymerism in normal individuals in patients with severe proteinuria and in normals with inhibited tubular protein reabsorption by lysine.

The polymeric forms of free kappa and lambda light chains were estimated in serum and urine from twelve normal individuals, from seven patients with nephrotic syndrome associated with normal GFR, and from eleven normal persons after inhibition of renal tubular protein reabsorption by lysine. The investigation showed that the serum concentrations of the monomeric and dimeric forms of light chains were similar in the three groups. The urinary excretion was increased in patients with nephrotic syndrome, the mean excretion of kappa chains being 9.2 mg/24 h and of lambda 6.6 mg/24 h compared with normal excretion of 2.2 mg/24 h for kappa and 1.0 mg/24 h for lambda. After inhibition of tubular protein reabsorption, the urinary light chains excretion increased to 101.3 mg/24 h for kappa and 40.0 mg/24 h for lambda chains, i.e. approximately 40 times normal level. The relative concentrations in the urine of the monomeric and dimeric forms of the two chain types were varied widely in the three groups investigated, particularly for lambda monomers where a low excretion rate and clearance value was found during inhibition of the protein reabsorption. The reason for the variations were found to be differences in polymerization and consequently differences in glomerular filtration. Evidence for a preferential reabsorption of any of the chain types or polymers was not seen.