ERGs in Streptozotocin-Diabetic Rats under Different Insulin Regimens

Abstract

It is generally hoped but not proved that good control of diabetes mellitus will delay the onset or stay the progression of diabetic retinopathy (DR). In order to obtain a better insight into this problem, we have tested the effects of different insulin injection regimens upon the development of retinopathy in Streptozotocin-diabetic female albino rats. Electroretinograms (ERGs) which are known to change in DR, were tested every two weeks in four groups of rats: 1. Normals; 2. Diabetic, no treatment; 3. Diabetic, treated with once-a-day injections of regular insulin, 10 units/kilogram (u/kg) body weight; and 4. Diabetic, treated with three 3.3 u/kg insulin injections every eight hours. Blood glucose, urine glucose and ketone levels, body weight and water intake were measured in all groups every two weeks. Animals were kept in semi-darkness, with food and water ad libitum. During four months following Streptozotocin injections in groups 2.-4., the diabetic (No. 2) no-insulin group behaved similarly to the diabetic (No. 3) once-a-day group of rats with respect to various ERG parameters and to other bodily assays. The normal (No. 1) and the thrice-a-day (No. 4) groups behaved similarly, with respect to both the ERG parameters and other assays. There were, however, highly statistically-significant (p<0.001) differences between the joint No. 2 and No. 3 groups on the one hand, and the joint No. 1 and No. 4 groups, on the other. In conclusion, the multiple-dose daily insulin therapy is far superior to the conventional therapy. A correlation of these results with the ongoing clinical trial of multiple-dose insulin therapy in human patients is discussed.

*

Supported by the Juvenile Diabetes Foundation.