A large increase in the ascorbic acid content has been shown to occur in the tissues of the white rat (able to synthesize that vitamin) after prolonged exposure and adaptation to cold (+ 4° to − 4 °C.). The increase in ascorbic acid is much smaller if the rats exposed to low temperatures receive daily supplements of that vitamin. On the other hand, a decrease in ascorbic acid content of the tissues has been found in rats unable to adjust themselves to cold environment. From the above results obtained with the white rat, it seems that the acclimatization to low temperatures—and not only maintenance of life at the same temperatures—requires large quantities of ascorbic acid.That conclusion was confirmed by experiments with guinea-pigs (animals that do not synthesize ascorbic acid); the results obtained show that resistance and adaptation of the guinea-pig to cold environment depend on the amount of ascorbic acid received daily; besides, during the process of acclimatization to cold, more ascorbic acid is retained in the tissues of the guinea-pigs exposed to low temperatures than in the same tissues of control animals kept at room temperature; finally, a direct relation has been observed between adaptability to cold environment and the content of ascorbic acid in the adrenals.
The purpose of this research was to investigate the relative value of different diets for conferring on animals resistance to extremes of temperature. These diets were equicaloric and equivitaminic and differed only in the relative proportions of fats, proteins, and carbohydrates. The self-selection method of feeding was used, with rats exposed to low and to high temperatures. The results obtained with this method have been verified on large groups of animals adapted and not adapted to extreme temperatures. It has been found that a diet rich in fats is decidedly superior to one rich in carbohydrates (both diets being equicaloric and equivitaminic) for adaptation and resistance to cold on the part of the animals, and that a diet rich in carbohydrates and poor in fats is much more favourable than one rich in fats for conferring resistance to heat.
It has been shown recently by Dugal and Thérien that during a short or long exposure to cold, the normal hypertrophy of the adrenals is completely prevented by large doses of ascorbic acid, and that, nevertheless, at the same time, resistance is increased towards the same damaging agent. So, the most universally accepted criterion of damage caused by stress is abolished when the animals exposed to cold receive large doses of ascorbic acid. Starting from that observation, it was natural to wonder what would be the effects of the ascorbic acid on the biological changes normally associated with the hypertrophy of the adrenals during exposure to cold. The present paper describes the experimental studies made in that connection; the results obtained show that: (1) ascorbic acid (a) partly inhibits the thymus atrophy normally encountered upon exposure to any stress including cold, (b) accelerates in a very significant way the enlargement of the thyroid, (c) is responsible for an increase in weight of the spleen, whereas the control animals, on the contrary, show a decrease in weight of the same organ; (2) the histamine content of the adrenals, which increases at room temperature under the influence of ascorbic acid, is significantly decreased during exposure to cold under the influence of the same substance; (3) the activity of the adrenals, far from being inhibited by ascorbic acid is even increased if the cholesterol changes are taken as an index of that activity; (4) the initial hypotension—due to cold—found in our controls, is prevented by large doses of ascorbic acid; on the other hand, if hypertension develops after long exposure to cold, the subsequent administration of large doses of ascorbic acid restores the blood pressure to normal. Confirmation has also been obtained for the previously reported observation that ascorbic acid prevents the hypertrophy of the adrenals during exposure to cold.
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