A review of the use of Streptozotocin (STZ) in the induction of diabetes in rats and subsequent ocular tissue changes

Abstract

Streptozotocin is widely used in medical research for treating certain cancers of the Islets of Langerhans and to produce an animal model for type 1 diabetes. A study has revealed that when compared to the control group of rats, those injected with STZ exhibited reduced plasma insulin and elevated blood glucose (p < 0.05 in all cases). The study also found that diabetic rats weighed significantly less than control animals (p < 0.05). In relation to ocular tissues, lacrimal glands from diabetic rats were also found to weigh significantly less  (p < 0.05) than those from the control group. However, no significant changes in the weights of lens, cornea, sclera and retina were observed between diabeticand control animals. Several other studies found that STZ-induced diabetes can be treated by plant extracts which control the blood sugar level as well as improving the lipid profile and ocular complications such as retinopathy. Experiments are usuallyperformed on male or female rats of a specific body weight, usually between 250 and 300 g. Diabetes is induced in rats by intraperitonial injections of streptozotocin (60 mg/ kg) in citrate buffer, pH 6.3.Animals that exhibit glucosuria after 24 hours, test-
ed by urine test strips are considered diabetic. Plant
extracts (6 mg/100g body weight) are orally administered into the stomach of STZ-diabetic rats every third day at a certain consistent time by means of bulbed steel needle for at least a four week period. This is done to determine the efficacy and potency
of the plant extracts on diabetes. Histological and transmission electron microscope (TEM) techniques are used to study the changes in the ocular tissues. The dissected ocular tissues should be dehydrated in graded ethyl alcohol series and embedded in Araldite CY212. Ultra thin sections should be contrasted with uranyl acetate and lead citrate for examination by TEM. Streptozotocin induces diabetes in laboratory animal models for scientific
studies and breakthroughs in medicine. The use of STZ and plant extracts may prove to be beneficial in the eye health care profession if considered for the studies of hypoglycemic agents that have the potency to prevent the advancement of diabetic retinopathy in diabetic patients.