A radioimmunometric assay for urinary alpha 2-macroglobulin.
To measure urinary alpha 2-macroglobulin levels, a sensitive radioimmunometric assay was established. The least detectable level of this assay was 225 pg/ml. A linear correlation between alpha 2-macroglobulin levels and serial dilution of urine samples was found. Western blot analysis and study on column chromatography revealed that the molecular weight of alpha 2-macroglobulin in urine was identical to that of serum alpha 2-macroglobulin. The findings suggested that urinary substance detected by the present assay was truly alpha 2-macroglobulin. Timed overnight urine samples from 49 diabetic patients with retinopathy and 20 healthy controls were measured by the present assay. Patients were classified as Albustix-negative and Albustix-positive patients. The highest urinary alpha 2-macroglobulin excretion rates (alpha 2-MER) was found in Albustix-positive patients followed by Albustix-negative patients and the healthy controls. In view of the fact that the stroke radius of alpha 2-macroglobulin (88A) is larger than that of the restrictive pore (56A), the present finding suggests that leakage of alpha 2-macroglobulin in urine may be induced by defect of non-discriminatory pores in the glomerular basement membrane proposed by Deen and colleagues.
Ito
S
S
Division of Gerontology, Akita University Hospital.
Usami
A
A
Yamazaki
M
M
Shibata
A
A
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000652:urine*; D005260:Female; D006801:Humans; D015592:Immunoradiometric Assay / Q000379:methods*; D008297:Male; D008832:Microchemistry; D008875:Middle Aged; D012016:Reference Values; D012680:Sensitivity and Specificity; D000511:alpha-Macroglobulins / Q000652:urine*
D000511:alpha-Macroglobulins