Enlargement of the juxtaglomerular apparatus in insulin-dependent diabetes mellitus patients with microalbuminuria.

Kidney biopsies from 15 insulin-dependent diabetes mellitus (IDDM) patients with microalbuminuria were investigated to obtain quantitative data on the juxtaglomerular apparatus. The IDDM patients were young and normotensive with a mean duration of microalbuminuria of 2 years. Eight healthy kidney donors served as controls. Measurements taken by light microscopy, using 1-microm serial sections of epon blocks, included volumes of the juxtaglomerular apparatus and of glomeruli, areas of the macula densa and luminal area of the juxtaglomerular (afferent and efferent) arterioles at the level of the glomerular vascular pole. The volume of the juxtaglomerular apparatus was significantly larger in the IDDM group than in controls [6.08 (2.96-18.8) 10(4) microm3 vs 3.48 (1.84-5.21) 10(4) microm3, P=0.003, median and (range)], as was the volume of the juxtaglomerular apparatus relative to glomerular volume [1.89(1.28-4.21)% vs 1.48 (1.13-1.71)%, P=0.004]. The area of the macula densa was also larger in the IDDM patients (1370 microm2 vs 937 microm2, P=0.03). Luminal areas of the afferent and efferent arterioles and the ratio between them did not differ significantly between the two groups. In conclusion, the juxtaglomerular apparatus is enlarged more than would be expected from the glomerular hypertrophy in IDDM patients with microalbuminuria.