title: Antioxidant effect of calcium antagonists on microsomal membranes isolated from different brain areas.
abstract: The antioxidant effect of Ca2+ antagonists on sheep brain microsomal membranes and on liposomes prepared with total lipids extracted from the membranes was studied. Microsomal membranes were isolated from three brain areas: frontal cortex, hippocampus and caudate nucleus. Lipid peroxidation was induced by ascorbic acid and measured by malondialdehyde formation. Seven Ca2+ antagonists representative of the major chemical classes (dihydropyridines, benzothiazepines, phenylalkylamines, alkylamines, diphenylpiperazines) were tested for their antioxidant activity over a wide range of concentrations (0-500 microM). The order of antioxidant activity on frontal cortex membrane phospholipids, expressed as 50% inhibition of peroxidation (antioxidant IC50), was: nifedipine (IC50 = 4 microM) greater than flunarizine (IC50 = 48 microM) greater than bepridil (IC50 = 50 microM) greater than verapamil (IC50 = 74 microM). The dihydropyridines, nitrendipine and nimodipine, and the benzothiazepine, diltiazem, did not affect peroxidation even at a concentration of 500 microM. Membrane phospholipids are the substrate for free radical-induced damage since the extent of peroxidation in brain microsomal membranes was equal to that produced in liposomes prepared from membrane lipids. Although the lipophilicity of certain Ca2+ channel antagonists can enhance their antioxidant activity, our data suggest that Ca2+ antagonists inhibit peroxidation of the membrane lipid bilayer by a free radical scavenger effect that may be related to their chemical structure.
authors.affiliation: Department of Zoology, Faculty of Medicine, University of Coimbra, Portugal.
authors.forename: T
authors.initials: T
authors.lastname: Gonçalves
authors.forename: A P
authors.initials: AP
authors.lastname: Carvalho
authors.forename: C R
authors.initials: CR
authors.lastname: Oliveira
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology; D001921:Brain / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002421:Caudate Nucleus / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects*; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D015394:Molecular Structure; D009928:Organ Specificity; D012756:Sheep; D013329:Structure-Activity Relationship
chemical_list: D000975:Antioxidants; D002121:Calcium Channel Blockers; D001205:Ascorbic Acid