Beta-2-microglobulin in sickle cell anaemia. Evidence of increased tubular reabsorption

Sickle cell nephropathy is characterized by severe defects in renal medullary functions. In contrast, both proximal tubular secretion and reabsorption are found to be elevated. Since proximal tubular cells are involved in reabsorption and catabolism of beta 2-microglobulin (beta 2-m), we studied serum concentration and urinary excretion of this low molecular weight protein in sickle cell nephropathy. Serum beta 2-m concentration was higher in sickle cell anaemia (SCA) patients compared to control persons. beta 2-m excretion, however, was normal and beta 2-m clearance was not significantly decreased. Fractional beta 2-m excretion was significantly lower and therefore tubular reabsorption of beta 2-m was increased in the SCA patients. There was no correlation between serum beta 2-m concentration and the tubular reabsorption of beta 2-m and phosphate. These findings are further evidence of a particular function of the proximal tubule in sickle cell nephropathy.