Histological and electron microscopic studies of the effect of beta-carotene on the pancreas of streptozotocin (STZ)-induced diabetic rats.

To evaluate the protective effect of beta-carotene on induction of diabetes by streptozotocin (STZ), 45 albino rats, weighed about 110-130 g were used. They were divided randomly into six groups. GI rats used as control; GII rats were injected i.p. with a single dose of 40 mg streptozotocin (STZ) to become diabetic; GIII and GIV, the diabetic rats were injected i.p. with 0.3 and 0.1 mg beta-carotene, respectively; GV and GVI rats were injected i.p. only with 0.3 and 0.1 mg beta-carotene respectively. At the end of the experiment, the final body weights, blood glucose and insulin levels were determined and the values were statistically analyzed. Histological, semithin and ultrathin sections were prepared for pancreatic tissues. In the diabetic rats (GII), there was significant loss in body weight accompanied by significant increase in blood glucose levels. In addition, many light and electron microscopic changes were observed in the acinar and endocrine beta-cells of islets of pancreas. These changes were summarized as disturbance of acini arrangement, shrinkage and pyknotic nuclei, vacuolation and dissolution of mitochondria and Golgi elements, degranulation of beta-cells. In addition to the significant decrease in blood glucose levels, 0.3 mg beta-carotene (Gill) had decreased most of these changes than 0.1 mg of it (GIV). So, GIII provides more protection for the pancreatic tissue more than GIV. Also, the results revealed that injection of rats only with 0.3 and 0.1 mg beta-carotene (GV and GVI) had no observable changes in the pancreatic tissues, except that there was an increase in number of the vacuolized mitochondria in most acinar and beta-cells of islets. In conclusions, 0.3 mg beta-carotene could normalize the biochemical disorders of diabetes and provides more protection for the pancreatic tissues than 0.1 mg from the damaging effect of STZ to a greater extent.