Urinary excretion of albumin and retinol-binding protein in lithium-treated patients: a longitudinal study.
The urinary excretion of albumin and retinol-binding protein was determined by means of sensitive immunochemical methods in a 2-year longitudinal study of 22 lithium-treated patients. During lithium treatment, there were no significant changes in the median albumin:creatinine ratios or retinol-binding protein:creatinine ratios. However, the median albumin:creatinine ratios were significantly higher in lithium-treated patients than in 22 normal subjects, which indicates that glomerular permeability is increased; no correlation with serum lithium level or duration of lithium treatment could be shown. In patients treated with slow-release tablets, the urinary excretion of albumin was significantly higher after 2 years than in patients given lithium carbonate. The median retinol-binding protein:creatinine ratios did not differ significantly between lithium-treated patients and normal subjects, suggesting that lithium does not affect the catabolism of low-molecular-weight proteins in the proximal tubules. In conclusion, the study supports the hypothesis that lithium treatment produces a small but significant and nonprogressive elevation of the urinary excretion of albumin.