Factors altering platelet monoamine oxidase. The influence of oral glucose intake.
The specific activity of human platelet monoamine oxidase from control subjects undergoing glucose tolerance tests is reduced drastically. Three hours after intake of 100 g of glucose only 25%-30% of the MAO-baseline activity was measured with tryptamine. beta-phenylethylamine and p-tyramine as substrates. At about 5 hr, platelet MAO activity has increased again. Inhibition was not due to small molecular weight inhibitors or other diffusible factors. Studies of other platelet enzymes, including succinate dehydrogenase and isocitrate dehydrogenase (NADP+ dependent) showed no parallel reductions; hGH, insulin, blood glucose and platelet glycogen concentrations did not correlate with platelet MAO activity. The changes of MAO activity in respect with p-tyramine and tryptamine as substrates 24 hr after glucose ingestion suggest changes of the lipid microenvironment of this enzyme of the outer mitochondrial membrane.
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001792:Blood Platelets / Q000201:enzymology*; D005947:Glucose; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007425:Intracellular Membranes / Q000201:enzymology; D007521:Isocitrate Dehydrogenase / Q000097:blood; D008297:Male; D008928:Mitochondria / Q000201:enzymology; D008995:Monoamine Oxidase / Q000097:blood*; D008996:Monoamine Oxidase Inhibitors; D013379:Substrate Specificity; D013385:Succinate Dehydrogenase / Q000097:blood
D001786:Blood Glucose; D007328:Insulin; D008996:Monoamine Oxidase Inhibitors; D007521:Isocitrate Dehydrogenase; D013385:Succinate Dehydrogenase; D008995:Monoamine Oxidase; D005947:Glucose