Pre- and post-treatment of streptozocin administered rats with melatonin: effects on some hepatic enzymes of carbohydrate metabolism.
BACKGROUND
Melatonin, found in high concentrations in the pineal gland, organs within the digestive system and in some plants and fungi, acts as an antioxidant which decreases reactive oxygen species in streptozocin-induced diabetic rats, raises insulin secretion by the pancreatic beta-cells and increases the number of insulin receptors on hepatocyte membranes.


METHODS
The protective and therapeutic effects of melatonin feeding in streptozocin-induced diabetic rats were studied. Streptozocin administered rats were gavaged with melatonin, pre- and post-treatment, at a level of 5 mg/kg body weight daily for a period of 15 days. Levels of plasma glucose, cholesterol, triacylglycerol, oral glucose tolerance test, and some hepatic enzymes of carbohydrate metabolism including insulin inducible glucokinase, hexokinase and glucose 6-P dehydrogenase were measured using standard methods and compared with the values in normoglycemic and diabetic control groups.


RESULTS
Both pre- and post-treatment of the streptozocin administered rats with melatonin normalized plasma glucose, cholesterol, and triacylglycerol, improved oral glucose tolerance test and increased hepatic glucokinase, hexokinase and glucose 6-P dehydrogenase specific activities to the levels seen in normal rats.


CONCLUSIONS
Melatonin pre-treatment prevents the injurious effects of streptozocin in rats. In streptozocin induced diabetic animals, post-treatment with this antioxidant normalizes both blood and liver constituents which were ameliorated by streptozocin.
Akmali
Masoumeh
M
Department of Biochemistry, Shiraz University of Medical Sciences, Shiraz, Iran. akmali34@yahoo.com
Ahmadi
Robab
R
Vessal
Mahmood
M
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use*; D001786:Blood Glucose / Q000032:analysis / Q000187:drug effects; D002784:Cholesterol / Q000097:blood; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000201:enzymology; D005941:Glucokinase / Q000187:drug effects; D005951:Glucose Tolerance Test; D005954:Glucosephosphate Dehydrogenase / Q000187:drug effects; D006593:Hexokinase / Q000187:drug effects; D008099:Liver; D008297:Male; D008550:Melatonin / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014280:Triglycerides / Q000097:blood
D000975:Antioxidants; D001786:Blood Glucose; D014280:Triglycerides; D002784:Cholesterol; D005954:Glucosephosphate Dehydrogenase; D006593:Hexokinase; D005941:Glucokinase; D008550:Melatonin