The vitamins A and C status of the rat and guinea pig, as influenced by the level of vitamins A and C intake, diet composition, calorie intake and exposure to cold.
Creators: name: Lachance, Paul A.
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 1969
Subjects: subject: Biology, Animal Physiology.

description: An enigma has existed since 1948 concerning the possible interrelationship of vitamin A and vitamin C. We first examined this possible relationship by taking advantage of the known effects of cold on tissue ascorbic acid. We found that vitamin A deficient rats had a decreased resistance to cold and that prior to becoming moribund, their vitamin C status was unaffected by the deficiency. The administration of vitamin C during the terminal stages of vitamin A deficiency did not alleviate the signs of vitamin A deficiency nor prolong survival in the cold. The data of the above experiments called our attention to the importance and necessity of utilizing the pair-feeding technique and a vitamin A deficient test diet of a different composition. We found that the onset of vitamin A deficiency at room temperature occurred ten days earlier on a yeast-free vitamin A deficient test diet. In addition, the control animals on the new diet had a distinct tendency for a better weight gain, a smaller liver and an increased liver storage of vitamin A. Exogenous vitamin C administered from the onset of the experiment did not retard nor ameliorate the course of the deficiency or the survival of rats fed either the U.S.P. or a yeast-free vitamin A deficient test diet. Administered vitamin C was readily taken up by the liver of rats on the yeast-free test diet but not by the liver of rats on the U.S.P. yeast-containing vitamin A deficient test diet. We believe this difference in composition of the test diets explains why a number of investigators were unable to find modifications in the ascorbic acid status of their animals after treatment with vitamin C. Pair-feeding adequately accounted for the decrease in liver reduced ascorbic acid which occurred in terminal vitamin A deficiency. Evidently, no relationship exists between the rat's resources of vitamin A and its capacity to synthesize ascorbic acid. Reduced glutathione does not seem to be the yeast factor which prevents the liver uptake of exogenous vitamin C. But, the administered reduced glutathione enhanced liver storage of vitamin A in normal rats and hastened the onset of the body weight gain plateau of vitamin A deficient rats by approximately five days. Guinea pig experiments demonstrated that treatment with moderate amounts of vitamin A did not hasten nor retard the development of scurvy. In addition, it was found that the absence of liver vitamin A in the guinea pig had no effect on the uptake and storage of supplemented vitamin C. Investigation into the beneficial effect of a high fat diet in the cold and the role of vitamins A and C revealed that increased fat in the diet exerts distinct beneficial effects in the cold, which are not enhanced when the diet is eaten in excess. We believe the mechanisms by which fat becomes a superior dietary constituent, are probably brought about by a conservation of energy resulting from a decrease in active lipogenesis and a decrease in specific dynamic action of non-fat foodstuffs. Fat promotes these decreases directly and also promotes an increased efficiency of the intestinal tract. The resultant energy conserved becomes available for heat production. In the cold, indications were found supporting the hypothesis that ascorbic acid may be intimately associated with some phase of fat metabolism. The requirement of vitamin A in the cold was noticeably increased on the high fat diet.