Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Because the significance of P-glycoprotein in the in-vivo secretion of beta-blockers in intestinal epithelial cells is unclear, the secretory mechanism for beta-blockers and other drugs has been evaluated. Uptake of the beta-blockers acebutolol, celiprolol, nadolol and timolol, and the antiarrhythmic agent, quinidine by the multidrug-resistant leukaemic cell line variant K562/ADM was significantly lower than that by drug-sensitive K562 cells, suggesting that these beta-blockers are transported by P-glycoprotein out of cells. The reduced uptake of acebutolol by the drug-resistant K562/ADM cells was reversed by treating the cells with anti-P-glycoprotein monoclonal antibody, MRK16, whereas no such alteration in uptake was observed for drug-sensitive K562 cells. Acebutolol uptake by K562/ADM cells was, moreover, markedly enhanced, in a concentration-dependent manner, in the presence of the specific P-glycoprotein inhibitors, MS-209 and cyclosporin. Caco-2 cells were used for evaluation of the role of P-glycoprotein in intestinal permeability to drugs in-vitro. Basolateral-to-apical transport of acebutolol was twice that in the reverse direction. A similar polarized flux was also observed in the transport of vinblastine, but not in that of acetamide or mannitol. When in-vivo intestinal absorption was evaluated by the rat jejunal loop method, with simultaneous intravenous administration of a P-glycoprotein inhibitor, cyclosporin, intestinal absorption of both acebutolol and vinblastine increased 2.6- and 2.2-fold, respectively, but no such enhancement was observed in the absorption of acetamide. The effect of cyclosporin on the intestinal absorption of several drugs was further examined, and the extent of the contribution of P-glycoprotein as an absorption barrier to those drugs was evaluated. ATP depletion by occlusion of the superior mesenteric artery resulted in a clear increase in epithelial permeability to vinblastine, but not to 3-O-methylglucose or acetamide, indicating that vinblastine is secreted by ATP-dependent P-glycoprotein into the lumen. These findings demonstrate that P-glycoprotein plays a role as an absorption barrier by transporting several drugs from intestinal cells into the lumen.
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PMID:Active secretion of drugs from the small intestinal epithelium in rats by P-glycoprotein functioning as an absorption barrier. 895 13

The purpose of this study is to characterize transport of acebutolol through the corneal epithelium. Cultured normal rabbit corneal epithelial cells (RCEC) were used to investigate the drug transport. Primary RCEC were seeded on a filter membrane of Transwell-COL insert coated with fibronectin and were grown in Dulbecco's modified Eagle's medium/nutrient mixture F-12 with various supplements. Measurements of acebutolol permeability through RCEC layer were carried out to assess transcellular permeability coefficient (P(transcell)) in the absence or presence of inhibitors. Paracellular permeability coefficient (P(paracell)) was calculated by permeability coefficient of hydrophilic drugs (P(cell)). The transcellular permeability of acebutolol from apical side to basal side (A-to-B) showed concentration-dependency. The acebutolol flux in the A-to-B direction was smaller than that of opposite direction. Sodium azide, verapamil, and cyclosporin A enhanced the transcellular permeability of acebutolol in the A-to-B direction. Acebutolol permeability through an excised rabbit cornea was also increased by verapamil. Thus, it was suggested that acebutolol was actively secreted via P-glycoprotein in a corneal epithelium.
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PMID:Transport of acebutolol through rabbit corneal epithelium. 1659 34