Examination of the molecular diversity of α ₁ antitrypsin in urine: Deficit of an α ₁ globulin fraction on cellulose acetate membrane electrophoresis

Abstract

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 α ₁ globulin (α ₁G) fractions, which contained α ₁AT in cellulose acetate membrane electrophoresis (CAE), tended to have α ₁ antitrypsin (α ₁AT) of normal molecular weight (57 kDa and 49 kDa), while patients with a deficit α ₁G fraction tended to have α ₁AT of low molecular weight (<49 kDa) ( P<0.01). The α ₁G fraction was significantly higher in patients with IgAN, and there were significantly more patients with normal molecular weight α ₁AT compared to patients with other diseases ( P<0.01). The isoelectric point of α ₁AT with lower‐weight molecules was more on the alkali side compared to higher‐weight molecules in two‐dimensional electrophoresis. Detecting changes in α ₁G fractions in CAE may support the differential diagnosis of IgAN from other types of GN. J. Clin. Lab. Anal. 19:16–21, 2005. © 2005 Wiley‐Liss, Inc.