Immunochemical Detection of Advanced Glycation End Products in Renal Cortex From STZ-Induced Diabetic Rat

To reassess the accumulation of advanced glycation end products in diabetic renal cortex, we used a newly developed enzyme-linked immunosorbent assay to measure AGEs in renal cortex from STZ-induced diabetic and age-matched control rats. Kidneys and aortas were obtained from rats after 5 and 20 wk of STZ injection. At 5 wk of diabetes, the mean AGE content in collagenase-digested materials of renal cortex was > 16-fold higher in diabetic animals compared with controls (1044.4 ± 151.8 vs. 64.3 ± 5.7 arbitrary units, P < 0.01). At 20 wk of diabetes, it was > 45-fold higher in diabetic compared with control animals (3841.0 ± 1077.3 vs. 83.8 ± 12.8 AUs, P < 0.01). These increases were surprisingly large compared with the < 1.5-fold increase in the fluorescence levels both after 5 and 20 wk of diabetes. In control animals, neither the AGE content nor the fluorescence level increased during this period. Moreover, at 20 wk of diabetes, the AGE content was 39-fold higher in renal cortex compared with aorta. This study provided the first immunochemical evidence that collagenase-digested materials of renal cortex, as well as aorta, contained AGE products and that these products were present in much higher levels in diabetic animals than in control animals. With duration of diabetes, the AGE contents increased significantly both in renal cortex and aorta. The excessive accumulation of AGEs was most apparent in the diabetic kidney. These findings suggest that the actual level of AGEs, in particular, in diabetic renal cortex is much higher than previously anticipated, and a newly developed enzyme-linked immunosorbent assay may be a powerful tool for investigating the role of the advanced Maillard reaction in the development of diabetic nephropathy.