STREPTOZOTOCIN-INDUCED DIABETES IN RATS IS ASSOCIATED WITH IMPAIRED METABOLIC AVAILABILITY OF VITAMIN-A (RETINOL)

Using streptozotocin-induced diabetic Wistar rats, studies were carrie d out to examine the metabolic availability of vitamin A in the plasma , liver and the retina of the eye, Control and diabetic rats were fed ad lib. on a semi-purified diet either with or without (basal) vitamin A supplementation, or pair-fed on the basal diet for 4 weeks, Despite the fact that diabetic rats consumed 48% more feed, they had lower pl asma concentrations of retinol (P < 0.003). The decrease in plasma ret inol concentration was a response to diabetes (or diabetes-induced tra uma), since neither pair-feeding (P < 0.01) nor vitamin A supplementat ion altered this effect (P < 0.05). Furthermore, the hepatic concentra tions of the vitamin in these animals remained elevated and this incre ase was greater in the supplemented diabetic group (P < 0.001). Decrea ses in 11-cis retinal (a component of rhodopsin) concentrations in the retina were also observed in diabetic animals. The increased hepatic and the decreased plasma and retina vitamin A levels suggest a defect in the transport of the vitamin from the liver.