Molecular heterogeneity of urinary albumin in glomerulonephritis: comparison of cardiovascular disease with albuminuria.
BACKGROUND
Despite the unstable structure of urinary albumin in kidney diseases, urinary albumin fragments have been identified by denaturing methods such as two-dimensional electrophoresis. This study examined the relationship between the structural heterogeneity of urinary albumin and protease effects.


METHODS
Urine samples from patients with glomerulonephritis (GN), cardiovascular diseases (CVD), and healthy subjects were analyzed by non-reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE), Western blot, diagonal 2-dimensional non-reducing/reducing (d2D) SDS PAGE, and albumin zymography.


RESULTS
The major band was monomer albumin in CVD and healthy subjects; however, 13 urinary albumin bands ranging from 55 to 172 kDa were identified by non-reducing SDS PAGE in GN. The results from d2D SDS PAGE showed urinary albumin polymerization between disulfide bridges, interactions with other proteins, and reduction induced degradation in GN patients. The results from albumin zymography showed that low-molecular mass forms of albumin did not necessarily correspond to high protease activity. Furthermore, concentrated healthy urine showed similar protease digestion as in GN without low-molecular mass of albumin.


CONCLUSIONS
The molecular alterations observed cannot be explained only by urinary proteases. The specific alteration of urinary albumin molecules in GN can be attributed to different mechanisms to CVD.
Nakayama
Aki
A
Division of Biomedical Laboratory Sciences, Graduate School of Health Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
Sakatsume
Minoru
M
Kasama
Takeshi
T
Kawara
Tokuhiro
T
Gejyo
Fumitake
F
Isobe
Mitsuaki
M
Sato
Kenji
K
Shiba
Kiyoko
K
D000328:Adult; D000418:Albumins / Q000032:analysis*; D000419:Albuminuria / Q000150:complications / Q000652:urine*; D015153:Blotting, Western; D002318:Cardiovascular Diseases / Q000150:complications / Q000652:urine*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005921:Glomerulonephritis / Q000652:urine*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010447:Peptide Hydrolases / Q000652:urine*
D000418:Albumins; D010447:Peptide Hydrolases