Abstract
The relationship of glomerular filtration and tubular reabsorption of albumin to urinary albumin excretion (UAE) was investigated in 42 NIDDM patients (DM) and 10 healthy controls (C) by inhibiting tubular reabsorption of albumin using 1-lysine loading. Based on the urinary albumin excertion rate (AER, μg/min), the NIDDM patients were divided into 3 groups: DM-I (n=22), AER<15 ; DM-II (n=13), AER 15-40 ; and DM-III (n=7), AER≥40, <200. Base-line AERs and the AERs after I-lysine loading (glomerular albumin excretion rate, GAE) were 6.7±0.84 (mean±SEM) and 180.4±8.3 in C, 6.2±0.8 and 180.7±10.6 in DM-I, 34.3±5.2 and 208.4±22.3 in DMII and 143.2±2.1 and 237.8±20.3 in DM-III. The baseline AER was correlated with GAE (r=0.366, p<0.05). The ratio (%) of albumin reabsorbed by tubules (GAE-baseline AER) to GAE was 96.3±0.5 in C, 96.5±0.4 in DM-I, 80.8±3.1 in DM-II and 40.4±7.3 in DM-III, and this ratio was inversely correlated with UAE (r=-0.933, p<0.001). In microalbuminuric patients with NIDDM, tubular reabsorption of albumin decreased as AER increased. These results suggest that in patients with AER≤40, the influence on UAE of decreasing tubular reabsorption was greater than that of increasing glomerular filtration, whereas the reverse was true in patients with AER>40, the influence on UAE of increasing glomerular filtration was greater than that of decreasing tubular reabsorption.
