RESUMO
We investigated the binding of radioactive carbamazepine and valproic acid to brain homogenates, lipid-free extracts, brain lipid, and phospholipid fractions. Carbamazepine was bound to each of these components in a manner that is qualitatively indistinguishable from the binding of phenytoin, in spite of major physical-chemical differences in these molecules but consistent with the similarities in pharmacologic action. These data support the concept that protein and phospholipid binding may be required for the activity of membrane-stabilizing anticonvulsants. Neither valproic acid nor its metabolites exhibited binding to brain or to any of the individual components tested. Therefore, binding cannot explain the reported long duration of action of this drug.
Assuntos
Encéfalo/metabolismo , Carbamazepina/metabolismo , Ácido Valproico/metabolismo , Animais , Autorradiografia , Cromatografia em Camada Fina , Técnicas In Vitro , Metabolismo dos Lipídeos , Camundongos , Proteínas do Tecido Nervoso/metabolismo , Fosfatidiletanolaminas/metabolismo , Fosfatidilserinas/metabolismo , Ligação Proteica , Coelhos , Esfingomielinas/metabolismo , UltrafiltraçãoRESUMO
The interaction of d-amphetamine with several brain tissue components has been investigated. A brain lipid extract and a number of individual phospholipids were found to bind d-amphetamine when measured by means of a hexane-buffer partition coefficient technique. Phosphatidylserine showed the greatest binding and phosphatidylethanolamine and dipalmitoyllecithin were also effective. Phospholipid binding of d-amphetamine was shown to be related to fatty acid composition. Cholesterol and ganglioside did not bind. It is suggested that phospholipid binding of d-amphetamine may play a role in the pharmacological action of this drug.
Assuntos
Encéfalo/metabolismo , Dextroanfetamina/metabolismo , Lipídeos de Membrana/metabolismo , Animais , Bovinos , Concentração de Íons de Hidrogênio , Modelos Químicos , Fosfolipídeos/metabolismo , Solubilidade , Relação Estrutura-AtividadeRESUMO
The binding of diphenylhydantoin-14C (DPH-14C) to several purified proteins and a number of tissue fractions from rats and rabbits has been studied by ultrafiltration and dynamic dialysis. In all cases the extent of binding correlated very closely with the protein concentration of the fraction investigated. Although binding to purified proteins varied considerably, binding to whole brain, subcellular fractions, liver, heart and kidney were identical. Skeletal muscle bound significantly less than other tissues. When brain homogenates were extracted with acetone or chloroform-methanol (2:1), the insoluble residue bound considerably greater amounts of DPH-14C per milligram of protein. Binding decreased after incubation with a proteolytic enzyme, but was not influenced by the addition of cations, ethylenediamine tetraacetic acid or ouabain. DPH-3H binding was constant over a large range of DPH concentrations (1 X 10(-10) to 2 X 10(-4)M) with no evidence for saturable or high affinity binding sites. It is suggested that tissue protein binding plays a role in the delayed attainment of adequate serum levels and the pharmacologic action of DPH.
