Glomerular charge selectivity in non-insulin-dependent diabetes mellitus.

To elucidate the stage of the charge selectivity defect in diabetic nephropathy, urinary excretions of IgG1 and IgG4 were measured in patients with non-insulin-dependent diabetes mellitus (NIDDM) and healthy controls. The molecular weights of IgG1 and IgG4 were the same but their isoelectric points were different. Therefore, by measuring both urinary IgG1 and IgG4 excretions, the stage of charge selectivity impairment in the nephropathy of NIDDM may be elucidated. Results were expressed as urinary excretion rate (IgG1 ER, IgG4 ER) and compared between diabetic patients with different urinary excretion rates of albumin (AER). IgG4 ER increased to the stage in which AER was more than 10 micrograms/min, whereas IgG1 ER did not increase to the stage of AER between 10 and 100 micrograms/min. This finding suggests that the charge selectivity defect in the kidney of the NIDDM patient is present at the stage when AER is more than 10 micrograms/min.