RESUMO
Intestinal efflux transporters can significantly reduce the absorption of the drug after peroral application. In this work we studied secretion of glutathione conjugates triggered by glucose at the luminal side of the intestine. Glucose stimulated secretion of DNPSG, NEMSG and CDNB. We used some different monosaccharides and determined that glucose, galactose and alpha-methylglucopyranoside trigger the secretion, while mannitol and fructose do not. We concluded that interaction with SGLT transporter is the key process necessary for this triggering. To determine which of possible glutathione conjugate transporters (MRP2, MRP4, BCRP or RLIP76) is responsible for the secretion of glutathione conjugates, we used benzbromarone, a MRP inhibitor, and sulfanitran and furosemide, two allosteric MRP2 activators. Benzbromarone inhibited glucose stimulated DNPSG secretion, while allosteric activators additionally increased the secretion. We concluded that MRP2 transporter is related to glucose stimulated DNPSG secretion. Regarding the work of Kubitz et al. we tested the effect of changed medium osmolarity on DNPSG transport and determined that hypoosmolar conditions trigger secretion of DNPSG. These findings suggest that intestinal MRP2 activity has no basal level, but can be stimulated by hypoosmolarity and SGLT transport.
Assuntos
Glutationa/análogos & derivados , Intestino Delgado/metabolismo , Monossacarídeos/metabolismo , Via Secretória/fisiologia , Transportadores de Cassetes de Ligação de ATP/agonistas , Transportadores de Cassetes de Ligação de ATP/antagonistas & inibidores , Animais , Benzobromarona/metabolismo , Polaridade Celular , Dinitroclorobenzeno/metabolismo , Enterócitos/metabolismo , Furosemida/metabolismo , Glucose/administração & dosagem , Glucose/metabolismo , Glutationa/química , Glutationa/metabolismo , Glutationa Transferase/metabolismo , Técnicas In Vitro , Masculino , Moduladores de Transporte de Membrana/metabolismo , Proteínas de Membrana Transportadoras/metabolismo , Metilglucosídeos/administração & dosagem , Metilglucosídeos/metabolismo , Monossacarídeos/administração & dosagem , Proteínas Associadas à Resistência a Múltiplos Medicamentos/agonistas , Proteínas Associadas à Resistência a Múltiplos Medicamentos/antagonistas & inibidores , Concentração Osmolar , Permeabilidade , Ratos , Ratos Wistar , Via Secretória/efeitos dos fármacos , Proteínas de Transporte de Sódio-Glucose/metabolismo , Succinimidas/metabolismo , Sulfanilamidas/metabolismoRESUMO
The growing concomitant consumption of drugs and herbal preparations such as garlic, and the numerous reports about the influence of herbal preparations on intestinal transport, led us to evaluate the influence of aged garlic extract on the transport function and electrophysiological parameters of the small intestinal mucosa. Aged garlic extract induced increase of the absolute value of the transepithelial potential difference and of the short-circuit current in both permeability models tested (rat jejunum, Caco-2 cell monolayers) without affecting transepithelial electrical resistance. It also caused a significant increase of the P-glycoprotein and multidrug resistance associated protein 2 mediated effluxes through rat jejunum of marker substrates Rhodamine 123 and 2,4-dinitrophenyl-S-glutathione, respectively. Rhodamine 123 efflux through the Caco-2 cell monolayers was not altered by aged garlic extract, whereas the efflux of 2,4-dinitrophenyl-S-glutathione increased significantly. So altered activity of the important transport proteins could significantly change the pharmacokinetic properties of conventional medicines taken concomitantly with aged garlic extract.
Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/fisiologia , Subfamília B de Transportador de Cassetes de Ligação de ATP/fisiologia , Alho/química , Animais , Transporte Biológico Ativo/efeitos dos fármacos , Células CACO-2 , Cromatografia Líquida de Alta Pressão , Cultura em Câmaras de Difusão , Eletrofisiologia , Fluoresceína , Glutationa/análogos & derivados , Glutationa/metabolismo , Humanos , Técnicas In Vitro , Mucosa Intestinal/metabolismo , Jejuno/metabolismo , Extratos Vegetais/farmacologia , Ratos , Rodamina 123 , Membro 4 da Subfamília B de Transportadores de Cassetes de Ligação de ATPRESUMO
Membrane transport characteristics of a paracellular permeability marker fluorescein were evaluated using artificial membrane, Caco-2 cell monolayers and rat jejunum, all mounted in side-by-side diffusion cells. Modified Ringer buffers with varied pH values were applied as incubation salines on both sides of artificial membrane, cell culture monolayers or rat jejunum. Passive transport according to pH partition theory was determined using all three permeability models. In addition to that, active transport of fluorescein in the M-S (mucosal-to-serosal) direction through rat jejunum was observed. The highest M-S P(app) values regarding the active transport through the rat jejunum were observed in incubation saline with pH 6.5. Fluorescein transport through the rat jejunum was inhibited by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) and alpha-CHC (alpha-cyano-4-hydroxycinnamic acid). Thus, we assume that two pH-dependent influx transporters could be involved in the fluorescein membrane transport through the intestinal (jejunal) epithelium. One is very likely an MCT (monocarboxylic acid cotransporter) isoform, inhibited by specific MCT inhibitor alpha-CHC, while the involvement of the second one with overlapping substrate/inhibitor specificities (most probably a member of the organic anion-transporting polypeptide family, inhibited at least partially by DIDS) could not be excluded.
