Examination of the molecular diversity of alpha1 antitrypsin in urine: deficit of an alpha1 globulin fraction on cellulose acetate membrane electrophoresis

In the clinical field of nephrology, a noninvasive approach employing the analysis of electrophoretic patterns in urinary protein has been established. In this study a total of 52 urine samples with IgA nephropathy (IgAN), anti-neutrophil cytoplasmic antigen-associated crescentic glomerulonephritis (GN), and other types of GN were analyzed. Patients with high alpha1 globulin (alpha1G) fractions, which contained alpha1AT in cellulose acetate membrane electrophoresis (CAE), tended to have alpha1 antitrypsin (alpha1AT) of normal molecular weight (57 kDa and 49 kDa), while patients with a deficit alpha1G fraction tended to have alpha1AT of low molecular weight (<49 kDa) (P < 0.01). The alpha1G fraction was significantly higher in patients with IgAN, and there were significantly more patients with normal molecular weight alpha1AT compared to patients with other diseases (P < 0.01). The isoelectric point of alpha1AT with lower-weight molecules was more on the alkali side compared to higher-weight molecules in two-dimensional electrophoresis. Detecting changes in alpha1G fractions in CAE may support the differential diagnosis of IgAN from other types of GN.