Relationship between mitochondrial lipid peroxidation and α-tocopherol levels in the guineα-pig adrenal cortex

Abstract

Lipid peroxidation in mitochondria from the functionally distinct inner (zona reticularis) and outer (zona fasciculate + zona glomerulosa) zones of the guinea-pig adrenal cortex was investigated. Ferrous ion (Fe 2+-induced lipid peroxidation was far greater in inner than outer zone mitochondria. Ascorbic acid similarly initiated lipid peroxidation to a greater extent in inner zone mitochondrial preparations. Differences in the unsaturated fatty acid content of inner and outer zone mitochondria could not account for the regional differences in lipid peroxidation. Total fatty acid concentrations were greater in the outer than in the inner zone, and the relative amounts of each fatty acid were similar in the two zones. However, mitochondrial concentrations of α-tocopherol, an antioxidant known to inhibit lipid peroxidation, were approx. 5-times greater in the outer than inner zone. The results demonstrate that there are regional differences in mitochondrial lipid peroxidation in the adrenal cortex which may be attributable to differences in α-tocopherol content. Thus, α-tocopherol may serve to protect outer zone mitochondrial enzymes from the consequences of lipid peroxidation and thereby contribute to some of the functional differences between the zones of the adrenal cortex.