Decrease In Catechol‐O‐Methyltransferase Activity In The Liver Of Streptozotocin‐Induced Diabetic Rats

Publisher Website
Google Scholar
Abstract
1. The present study compared the activity of catechol‐ O‐methyltransferase (COMT) in the liver and plasma of streptozotocin (STZ)‐induced diabetic rats with that in normal rats. The activity of COMT was estimated by the metabolism of noradrenaline to metanephrine (MN), both measured by high‐performance liquid chromatography with electrochemical detection. 2. Formation of MN was decreased in the liver of STZ‐ diabetic rats compared with normal rats. The amount of MN was also decreased in plasma obtained from STZ‐diabetic rats. A Michaelis–Menten plot showed a reduction in the maximum velocity and an increase in the Km for COMT in liver samples from STZ‐diabetic rats. 3. The role of hyperglycaemia in the lowering of COMT activity was then investigated using phlorizin or insulin at doses sufficient to normalize plasma glucose from STZ‐diabetic rats. Both insulin and phlorizin treatment of STZ‐diabetic rats for 4 days restored the activity of COMT to that seen in normal rats. Thus, correction of hyperglycaemia in STZ‐diabetic rats can reverse the decrease in COMT activity. The activity of COMT is lower in STZ‐diabetic rats than in normal rats mainly due to the higher plasma glucose.