BM thickening in retinal and glomerular capillaries developed in a correlated manner during 6 months of streptozotocin-induced diabetes (
r = 0.79,
P = 0.0001;
Figs. 1A 1B ). The mean BM thickness of retinal and glomerular capillaries was significantly increased in the D rats compared with those of N rats (69.2 nm vs. 50.8 nm,
P < 0.02; 111.4 nm vs. 81 nm,
P < 0.02, respectively), a 36% and 38% increase, respectively. The BM thickness of retinal and glomerular capillaries of TC rats was slightly increased (5.5% and 7.0%, respectively) but not statistically significant, compared with those of N rats (53.6 nm vs. 50.8 nm,
P = 0.28; 86.7 nm vs. 81 nm,
P = 0.25;
Fig. 1C ). The data on retinal and glomerular capillary BM thickness of each animal is presented in
Figure 1B . Although the percentage increase in BM thickness during the 6 months of diabetes was similar for retinal and glomerular capillaries in the D rats (43% vs. 40.5%, adjusted for aging, respectively), the actual capillary BM thickening in the two tissues was different; the retinal capillaries thickened by an average of 26.2 nm whereas the glomerular capillaries thickened by 41.4 nm. The BM thickness of glomerular capillaries was consistently greater than those of the retinal capillaries. On the basis of the baseline values obtained at the start of the study for retinal and glomerular capillary BM thickness (43 ± 7 nm, 74 ± 5 nm, respectively) compared with the BM thickness after 6 months (50.8 and 8 nm, respectively), aging and other nondiabetic factors appear to have contributed to overall BM thickening by approximately 18% and 10% in these two tissues, respectively.