Morphological change of microvilli in proximal tubule is correlated with the change of α-actinin 4. Electron microscopic appearance of microvilli of the tubules (A, B) and immuno-electron microscopic localization of α-actinin 4 in microvilli (C, D) and in the adherins junction (F, G) of tubules. (A, B) Comparison of electron micrographs of proximal tubules from nondiabetic rat (A) and diabetic rat (B) revealed that microvilli of the diabetic rat were swollen and had become bulbous, whereas those of the Wistar rat were regularly shaped. (C, D, F, G) Sections of nondiabetic and diabetic kidneys were immunolabeled for α-actinin 4 (12-nm gold particles). Whereas only a few gold particles were localized in the microvilli of proximal tubules in the nondiabetic kidney, many gold particles were detected in the microvilli of proximal tubules in the diabetic kidney (C, D). (E) Density (number/μm2) of colloidal gold particles representing α-actinin 4 in the microvilli from nondiabetic (open bar) diabetic kidney (closed bar) kidneys. Data are the means ± SEM from 3 different rats. *P < 0.01 vs. control (Wistar rat). (F, G) The colloidal gold labels indicating α-actinin 4 were also observed in the adherins junction of proximal tubules of both nondiabetic (F) and diabetic (G) kidneys. Scale bars: 200 nm (A, C) and 100 nm (F).