title: The composition of the incubation medium influences the sensitivity of mitochondrial permeability transition to cyclosporin A.
abstract: The aim of this work was to study permeability transition, and the influence of the composition of the incubation medium, on the inhibitory action of cyclosporin A. It was found that cyclosporin inhibited the opening of a nonspecific pore, as induced by the uncoupler carbonyl cyanide m-chlorophenylhydrazone, provided K+ was present in the incubation medium, but failed to do so if mitochondria are incubated in sucrose or Na+-based medium. It was also found that the sensitivity of mitochondria to the uncoupler depended on the incubation mixture, being more sensitive when sucrose was the osmotic support. Matrix Ca2+ release, large amplitude swelling, and drop in transmembrane electric gradient revealed permeability transition. The titration of membrane thiol groups shows them to be increased in mitochondria incubated in sucrose medium, in comparison with the values found in mitochondria incubated in KCl or NaCl medium. Our proposal is that the incubation in sucrose medium propitiated a conformational change of membrane proteins in such a way that cyclosporin was unable to bind to its target site.
authors.affiliation: Departamento de Bioquímica, Instituto Nacional de Cardiología Ignacio Chavez, 014080 Mexico, D.F,. México. echavez@ssa.gob.mx
authors.forename: Edmundo
authors.initials: E
authors.lastname: Chávez
authors.forename: Noemi
authors.initials: N
authors.lastname: García
authors.forename: Cecilia
authors.initials: C
authors.lastname: Zazueta
authors.forename: Francisco
authors.initials: F
authors.lastname: Correa
authors.forename: César
authors.initials: C
authors.lastname: Avilés
authors.forename: Gerardo
authors.initials: G
authors.lastname: García
authors.forename: Eros O
authors.initials: EO
authors.lastname: Balam
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects* / Q000502:physiology*; D002478:Cells, Cultured; D003470:Culture Media / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D016062:Porosity; D011188:Potassium / Q000378:metabolism*; D012680:Sensitivity and Specificity; D012964:Sodium / Q000378:metabolism*; D013395:Sucrose / Q000378:metabolism
chemical_list: D003470:Culture Media; D013395:Sucrose; D016572:Cyclosporine; D012964:Sodium; D011188:Potassium; D002118:Calcium