GLOMERULAR STRUCTURE IN TYPE-1 (INSULIN-DEPENDENT) DIABETIC-PATIENTS WITH NORMOALBUMINURIA AND MICROALBUMINURIA

Kidney biopsies from 15 type-1 (insulin-dependent) diabetic patients with a range of albumin excretion (AER) were analyzed. Nine patients had normal AER, and six had microalbuminuria. Basement membrane thickness, BMT, and mesangial matrix volume fraction, V(v)(mat/glom), were obtained from at least three glomeruli per biopsy. Mesangial structures were estimated with electron microscopic analysis at three levels in each glomerulus. Glomerulopathy parameters were significantly increased in microversus normoalbuminuric patients with the following means and (CV): BMT 571 nm (0.12) and 442 nm (0.25), P = 0.03; V(v)(mes/glom) 0.31 (0.20) and 0.22 (0.14), P = 0.002; V(v)(matrix/glom) 0.17 (0.25) and 0.11 (0.28), P = 0.006; matrix star volume 56-mu-m3 (0.47) and 22-mu-m3 (0.43), P = 0.02. A positive correlation obtained between AER and each of the glomerulopathy parameters, BM thickness, V(v)(mes/glom) and V(v)(matrix/glom), as well as between AER and a structural index expressing the sum of changes in the peripheral BM and in the mesangium (r = 0.62, P = 0.01). The results indicated a parallel course of mesangial and peripheral BM changes: a positive correlation obtained between BM thickness and mesangial parameters [BMT versus V(v)(matrix/glom): r = 0.82, P = 0.0001] and the ratio of the two subsets of glomerular BM material (PBM:matrix) did not show significant difference between normo- and microalbuminuric groups. The data give strong support to the contention that the transition from normo- into the microalbuminuric phase is linked to progressing glomerulopathy.