On the protection by inorganic phosphate of calcium-induced membrane permeability transition.
The role of inorganic phosphate as inhibitor of mitochondrial membrane permeability transition was studied. It is shown that in mitochondria containing a high phosphate concentration, i.e., 68 nmo/mg, Ca2+ did not activate the pore opening. Conversely, at lower levels of matrix phosphate, i.e., 38 nmol/mg, Ca2+ was able to induce subsequent pore opening. The inhibitory effect of phosphate was apparent in sucrose-based media, but it was not achieved in KCI media. The matrix free Ca2+ concentration and matrix pH were lowered by phosphate, but they were always higher in K+-media. In the absence of ADP, phosphate strengthened the inhibitory effect of cyclosporin A on carboxyatractyloside-induced Ca2+ efflux. Acetate was unable to replace phosphate in the induction of the aforementioned effects. It is concluded that phosphate preserves selective membrane permeability by diminishing the matrix free Ca2+ concentration.
Chávez
E
E
Departamento de Bioquímica, Instituto Nacional de Cardiología, Ignacio Chávez, México, DF, México.
Moreno-Sánchez
R
R
Zazueta
C
C
Rodríguez
J S
JS
Bravo
C
C
Reyes-Vivas
H
H
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016572:Cyclosporine; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010539:Permeability / Q000187:drug effects; D010710:Phosphates / Q000494:pharmacology*; D051381:Rats; D012965:Sodium Chloride / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology
D010710:Phosphates; D012965:Sodium Chloride; D013395:Sucrose; D016572:Cyclosporine; D002118:Calcium