The action of l-ascorbic acid on the in vitro respiration of liver tissue from guinea-pigs on a restricted diet. II

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Abstract
The addition of low concs, of Z-ascorbic acid increased the rate of respiration of surviving liver tissue from about 95% of guinea-pigs maintained on a quantitatively restricted diet containing more than enough vit. C to protect from macroscopic and microscopic lesions of scurvy. Even the resp. of liver tissue from guinea-pigs on a restricted diet fully saturated in respect to vit. C, behaved in this way. The liver tissue of only about 30% of animals on a normal diet responded to the addition of Z-ascorbic acid. Compounds chemically related to Z-ascorbic acid such as d-glucoascorbic acid and reductic acid, which possess reduction potentials of the same order as Z-ascorbic acid but no antiscorbutic activity, also stimulated the resp. of liver tissue from guinea-pigs on a restricted diet. Added Z-ascorbic acid or analogs is lost during the process of resp., but the loss is less than equivalent to the increase in Q02 on the assumption that they are oxidized to oxalic and Z-threonic acids, nor do measurements of CO2 production suggest complete breakdown of the acid. The increase in resp. was largely abolished by phloridzin, pyrophosphate and hydroxymalonate; it was not affected by maleate, arsenite, malonate or cinnamate. Iodoacetate depressed the Q02 value of liver tissues from normal animals but the addition of Z-ascorbic acid prevented this inhibition. Fluoride decreased the respiration of liver tissues from animals on a restricted diet in the absence, but not in the presence, of Z-ascorbic acid. The relative increase in Qo* produced by added Z-ascorbic acid was unchanged by cyanide. The bearing of these results on the possible connexion between the accelerating effect of added Z-ascorbic acid on the resp. of liver tissue from guinea-pigs on a restricted diet and their carbohydrate metabolism is discussed.

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