Activity Changes of Molybdenum Hydroxylases in Liver, Kidney and Jejunum of Streptozotocin- Induced Diabetic Rats

The aim of this study is to investigate the effect of diabetes induction on the specific activity of two molybdenum hydroxylases, namely aldehyde oxidase and xanthine oxidase. Streptozotocin in asingle i.p. injection (65 mg/kg) induced diabetes in male Wistar rats as indicated by a sharp and significant increase of plasma glucose level after 5 days of the treatment. Three tissues (liver, kidney and jejunum) were excised and assayed for the activity of aldehyde oxidase and xanthine oxidase. Two substrates (phthalazine and 3-methylisoquinoline) were used to measure aldehyde oxidase activity, while xanthine was used for xanthine oxidase. Hepatic aldehyde oxidase activity was increased significantly (P 0.025) in diabetic rats as compared to controls when phthalazine was used as a substrate. The other two tissues (kidney, jejunum) did not show any significant variation in aldehyde oxidase activity when diabetic and control rats were compared. No significant change of this enzymic activity was noted in the three tissues (liver, kidney and jejunum) when 3-methylisoquinoline was used as a substrate. On the other hand, xanthine oxidase activity in liver and jejunum was markedly decreased (P 0.005 and P 0.0005, respectively) in diabetic rats while the enzymic activity of kidney remained unchanged. These results suggest the presence of multiple isomeric forms of molybdenum hydroxylases and some of these forms can be induced or suppressed by the diabetic inducingagent streptozotocin.