Enhancement of free radical reduction by elevated concentrations of ascorbic acid in avian dystrophic muscle.

It has been postulated that the degenerative process in dystrophic muscle results from increased concentrations of free radicals, peroxides, or lipid hydroperoxides. Therefore, the reduction of the free radical tanol (2,2,6,6-tetramethyl-4-piperidinol-1-oxyl) by extracts of muscles of dystrophic and normal chickens was studied. Pectoral (white) and thigh (red) muscles were used. For initial rate measurements, the various muscle extracts were added to an equal volume of 0.2 mM tanol. Reaction mixtures were introduced into the EPR cavity in a standard aqueous flat cell. Rates were measured by continuously monitoring the decrease in signal amplitude of the center (MI = 0) solution tanol EPR resonance line (in-phase first harmonic absorption signal). With extracts from dystrophic white muscle, the reduction rate was 75% faster than normal, whereas in dystrophic red muscle extracts the rate was normal. This agreed with previous observations that white muscle is more severely affected than red in dystrophic chickens. The primary reductant was identified as reduced ascorbic acid, and the rate of reduction of tanol correlated directly with the concentrations of ascorbic acid in the various muscle extracts as shown by chemical analysis. The results suggest an involvement of the intracellular redox status in the pathogenesis of avian muscular dystrophy.