A QUANTITATIVE ULTRASTRUCTURAL-STUDY OF JUXTAGLOMERULAR ARTERIOLES INIDDM PATIENTS WITH MICROALBUMINURIA AND NORMOALBUMINURIA

Hyalinization of juxtaglomerular arterioles is prominent in advanced d iabetic nephropathy and may have important functional consequences. We studied the early stages of diabetic renal disease using kidney biops y material from insulin-dependent diabetic patients, 8 with normal alb umin excretion rate (< 15 mu g/min) and 16 with microalbuminuria (15-2 00 mu g/min). Ten living non-diabetic kidney donors served as a contro l group. Median duration of diabetes was 9.5 years (range 5-31) in pat ients with normoalbuminuria, and 12 years (7-22) in patients with micr oalbuminuria (p = 0.27). The tissue was sectioned systematically, 1-mu m thick sections for light microscopy at 10-mu m intervals, and thin sections for electron microscopy taken at 60-mu m intervals. The arter ioles were identified as afferent or efferent, and total profiles were photographed (magnification 7500 x), providing a systematic independe nt sample for measurements using standard stereological methods. Patie nts with microalbuminuria had significantly increased arteriole parame ters compared with the control group: for afferent and efferent arteri oles the volume fraction of matrix/media, means and (coefficient of va riation, CV), was 0.37 (0.16) vs 0.33 (0.19) (p = 0.0009), and 0.62 (0 .14) vs 0.45 (0.23) (p = 0.0004) and matrix-T, expressing amount of ma trix per unit arteriolar surface, 2.38 (0.38) mu m vs 1.44 (0.30) mu m (p = 0.004), and 1.62 (0.28) mu m vs 1.03 (0.34) (p = 0.0009). Patien ts with normoalbuminuria showed no significant differences from the co ntrol group, and had lower values than microalbuminuric patients for a ll parameters except the afferent matrix-T. In the normoalbuminuric gr oup a correlation was found between parameters for afferent arterioles and those for glomerular structure. In conclusion there is arteriolar accumulation of extracellular material in the early phase of diabetic nephropathy, concomitant with early glomerulopathy.