Abstract
Summary
Cell-free thymic extracts (thymic humoral factor or THF) were prepared from guinea pigs maintained 6 weeks on daily intakes of 0.25, 0.50, 1.00, or S.00 mg of vitamin C. The concentration of dehydroascorbate in their thymuses increased, and that of ascorbate (and total vitamin C) decreased in direct proportion to the level of vitamin C in the diet. The activity of each preparation was then compared by measuring regeneration of lymphoid organ weight and hexose monophosphate shunt enzyme activity in irradiated, THF-injected rats, and was found to be directly correlated with the level of ascorbate, and inversely correlated with the level of dehydroascorbate in the THF preparations. Thus the data indicate that throughout the ontogeny of the thymus, the level, and particularly the oxidation state of thymic vitamin C is involved in some manner for the production of THF. No evidence was found that vitamin C was required for the actual expression of THF activity, since prior to bioassay, the partial removal of ascorbic acid from similarly prepared rat THF preparations did not result in diminished reponses.
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