Inhibition of active-transport sodium-potassium-A.T.P.ase by myeloma protein

Patients with multiple myeloma excrete immunoglobulin light chain (Bence-Jones protein) in the urine. Light chain accumulates in the nephron, and this may result in renal disease, which accounts for the death of between 1 in 4 and 1 in 7 patients with multiple myeloma. Myeloma light chain inhibits transport of paraaminohippurate in the kidney. Evidence is presented here that light chain affects renal transport by inhibiting the active-transport enzyme, ouabain-sensitive Na-K-A.T.P.ase. As a direct consequence, renal A.T.P. content and the maximum rate of gluconeogenesis from lactate are enhanced in the presence of light chain.