Effects of benzo[a]pyrene on steady-state levels of biogenic amines and metabolizing enzymes in mouse brain regions.
Benzo[a]pyrene (BaP) is a product of incomplete fossil fuel combustion, a well-known pollutant, and a carcinogenic agent. In the present study male CD-1 mice received ip injections of 0, 5, 25, and 100 mg/kg body weight BaP twice a week for 3 weeks. Endogenous levels of brain biogenic amines and their selected metabolites, norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT), vanillylmandelic acid, dihydroxyphenylacetic acid (DOPAC), homovanillic acid, and 5-hydroxyindoleacetic acid (5-HIAA) were measured using high performance liquid chromatography and electrochemical detection. The brain regions studied were cortex, striatum, hypothalamus, midbrain, medulla oblongata, and cerebellum. BaP treatment increased the steady-state levels of NE, DA, and 5-HT in the hypothalamus and striatum. Increased levels of DA and 5-HT and their major metabolites DOPAC and 5-HIAA were noticed in the same region, an indication of increased metabolism of these amines. The increase in the 5-HT level in the cortex was not dose-related. Levels of NE and DA were significantly higher in the medulla oblongata. There was a concurrent increase in activities of tyrosine hydroxylase and tryptophan hydroxylase in several brain regions. The effect of BaP on Dopa-decarboxylase was not consistent. Monoamine oxidase was occasionally inhibited. Results indicate that exposure to BaP altered the steady-state levels of biogenic amines in various brain regions and these changes were consistent with the activities of metabolizing enzymes.
Jayasekara
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Department of Biology, Utah State University, Logan 84322.
Sharma
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Drown
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D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D001679:Biogenic Amines / Q000378:metabolism*; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004296:Dopa Decarboxylase / Q000378:metabolism; D008297:Male; D051379:Mice; D008995:Monoamine Oxidase / Q000378:metabolism; D014365:Tryptophan Hydroxylase / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D001679:Biogenic Amines; D001564:Benzo(a)pyrene; D014446:Tyrosine 3-Monooxygenase; D014365:Tryptophan Hydroxylase; D008995:Monoamine Oxidase; D004296:Dopa Decarboxylase