IngentaConnect Decrease In Catechol-O-Methyltransferase Activity In The Liver Of...

Authors: Wang, JP¹; Liu, IM²; Tzeng, TF³; Cheng, JT²

Source: Clinical and Experimental Pharmacology and Physiology, Volume 29, Numbers 5-6, May/June 2002 , pp. 419-422(4)

Publisher: Blackwell Publishing

Abstract:

SUMMARY

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 K_m 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.

Keywords: catechol-O-methyltransferase; insulin; metanephrine; phlorizin

Document Type: Research article

DOI: 10.1046/j.1440-1681.2002.03673.x

Affiliations: 1: Department of Orthopedics, Mackay Memorial Hospital, Taipei City, 2: Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan City and 3: Department of Internal Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung City, Taiwan, ROC

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