Effects of oxygen and antioxidants on the mitochondrial Ca-retention capacity.
Arch Biochem Biophys
; 306(1): 139-47, 1993 Oct.
Article
en En
| MEDLINE
| ID: mdl-8215394
ABSTRACT
2-Oxoglutarate-supported rat liver mitochondria were loaded with moderate amounts of calcium and submitted to O2 deprivation and reoxygenation. In the presence of acetoacetate, anaerobic energy production maintained Ca2+ retention by mitochondria during the anoxia period unless the Pi concentration of the incubation solution was raised to 4-6 mM. Acetoacetate prompted Ca2+ release from O2-deprived mitochondria at elevated Pi levels, presumably due to occurrence of a permeability transition of the inner membrane. Providing 3-hydroxybutyrate and malate, together with acetoacetate, was found to delay the permeability transition until O2 was reintroduced, i.e., O2 triggered a paradoxical release of Ca2+ from mitochondria under these conditions. Whether initiated by O2 in the presence of Pi or by Pi under aerobic conditions, Ca2+ release was initially activated and subsequently inhibited or reversed in the presence of alpha-tocopherol (10-90 mumol.g protein-1). Similar effects were exerted by alpha-tocopherol during Pi-induced Ca2+ release from oligomycin-treated mitochondria supported by succinate (+ rotenone). In addition, the permeability transition was delayed by retinol (3-30 mumol.g protein-1) while beta-carotene, ubiquinone, and water-soluble antioxidants, including Trolox C, were ineffective. Other observations suggest that the Ca(2+)-releasing and/or -retaining effects of alpha-tocopherol and retinol may be independent from pro- and/or antioxidant activities. Effects resembling those of alpha-tocopherol were exerted by alpha-tocopherol succinate, which is devoid of antioxidant activity. Our data indicate that the permeability transition of Ca(2+)-loaded liver mitochondria may be triggered by O2, in the presence of ketone bodies, and affected by lipid-soluble antioxidants through mechanisms seemingly unrelated to free-radical generation or scavenging.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Oxígeno
/
Mitocondrias Hepáticas
/
Calcio
/
Antioxidantes
Límite:
Animals
Idioma:
En
Revista:
Arch Biochem Biophys
Año:
1993
Tipo del documento:
Article
País de afiliación:
Suiza