Beta-carotene 15,15'-dioxygenase activity in streptozotocin-induced diabetic rats

We measured retinol levels and beta-carotene 15,15'-dioxygenase activity in rats with streptozotocin-induced diabetes mellitus to assess the relationship between the disease and the conversion of beta-carotene to retinol. The plasma retinol level was significantly lower in diabetic rats than in control rats, but the hepatic retinol level was significantly higher than the control. The hepatic dioxygenase activity, but not that of the intestinal mucosa, was significantly lower in diabetic rats than in control rats. The hepatic dioxygenase activity showed a significant negative correlation with the hepatic retinol levels. The results suggest the disturbed secretion of retinol from the liver and suppression of hepatic dioxygenase activity by the retinol increased in the liver in diabetic rats.