Calmodulin glycation in diabetic rat lenses

The activation of phosphodiesterase by calmodulin isolated from diabetic rat lens tissue was determined. Male rats, 200-250 g, were rendered diabetic by injection of streptozotocin (45 mg/kg body weight) via the tail vein. After the onset of diabetes, the animals were observed for 15 weeks. Compared with a blood glucose level of 94.84 +/- 2.72 mg/dL in the control group, 1, 4, and 6 week diabetic rats had blood glucose levels of 357.00 +/- 7.55, 366.53 +/- 4.76, and 366.57 +/- 5.30 mg/dL, and 8, 10, and 15 week diabetic rats had levels over 400 mg/dL. After collecting the lens tissue, boiled extracts were prepared as a calmodulin source and were applied to a Glycogel B column for separating glycosylated and nonglycosylated calmodulin. Calmodulin activities of boiled extracts and glycosylated eluates were determined via the activation of calmodulin-deficient brain phosphodiesterase. Calmodulin activities of diabetic rat lenses were significantly reduced compared with the control group. The results of glycosylated protein determination with the thiobartiuric acid method were in accordance with calmodulin activities. Calmodulin activities of the diabetic lens tissues were reduced, while the protein glycosylation levels were elevated.