SDS-PAGE PATTERNS AND POLYMERIC ALBUMIN IN PROTEINURIA OF LUPUS GLOMERULONEPHRITIS

Proteinuria was characterized by SDS-PAGE and by immunoblotting with antihuman albumin sera for the detection of urinary polymers of albumin (PA) in 40 patients with biopsy proven lupus glomerulonephritis (LN) (6 pts class III WHO, 24 pts class IV, 10 pts class V) with various clinical presentations (nephrotic syndrome with normal or impaired renal function, 14 pts; urinary abnormalities with normal or impaired renal function, 21 pts; clinical remission, 5 pts); in 25 pts, for whom the characterization of proteinuria and the renal biopsy were performed at the same time, the activity and chronicity index scores were calculated. The mixed SDS-PAGE patterns, characterized by the presence of low molecular weight proteins, were the more frequently found; the mixed patterns were significantly associated with interstitial Leukocyte infiltration (p = 0.05) and glomerular sclerosis (p = 0.046) and nonsignificantly associated with higher values of serum creatinine; no SDS-PAGE pattern had predictive value on functional outcome at 36 months. Albumin polymers were present in 67% of pts; in active disease they were present in 33% of class III, in 100% of class IV and in 45% of class V WHO (p = 0.026); PA were not present in 5 pts with clinical remission (4 class IV and 1 class V WHO). The presence of PA was significantly associated with high values (>10) of activity index (p = 0.009) and with extracapillary proliferation (p = 0.041). Serum creatinine tvas lower in patients without PA (Scr 1.0 +/- 0.4 mg/dl) than in those with PA (Scr 1.5 +/- 1.0 mg/dl), but the difference was not statistically significant. At 36 months pts without PA had normal and stable renal function, while patients with PA showed a trend toward renal function deterioration (Scr from 1.5 +/- 1.0 to 1.9 +/- 1.4) but the difference was not statistically significant. In summary, the characterization of proteinuria allow to distinguish various patterns, some of which are correlated with some histological parameters and with renal functional impairment and might be considered biochemical markers of disease severity,