Serum beta2-microglobulin in hemodialyzed patients.

beta2-Microglobulin (beta2-M) concentrations were measured by radioimmunoassay in 63 patients treated with maintenance hemodialysis. Serum levels ranged from 12.5 to 92 microgram/ml and were found stable upon sequential measurements over a 6-month period. Excretion of beta2-M was achieved through urinary loss (up to 150 mg/day) and to a lesser extent by ultrafiltration across acrylopolynitrile but not cellophane dialysis membranes. Proximal tubular cells being the major site of beta2-M catabolism, stable levels in anephric patients indicated a defective production of beta2-M in uremic patients. Serum beta2-M levels were not correlated with predialysis urea, creatinine, hematocrit or middle molecule material. In vitro experiments do not support a possible toxicity of purified beta2-M but do not rule out the contribution of other low molecular weight proteins to uremic toxicity.