Abstract
In an attempt to analyse factors affecting adaptative change of basal metabolism, experiments were designed to be performed with groups of rats which were acclimated in cold (5°C), control (20°C) and hot (30°C) chamhers respectively. Each temperature groups was subdivided into different food groups, ie. high fat, high carbohydrate (CHO) and high protein group. Results obtained are as follows:
1) The thyroid activity was demonstrated to be accelerated significantly in the high fat subgroup in heat as well as cold acclimation, while the high CHO subgroup showed a lower thyroid activity in heat acclimation as compared to that in cold acclimation.
2) The resting O2 consumption was reduced in heat acclimation, while increased in cold acclimation. The reduction rate of O2 consumption in heat acclimation was striking in high CHO subgroup, while less in high fat subgroup. The O2 consumption of high fat subgroup in control temperature was also higher than that of CHO subgroup.
3) From these experimental results, it may be concluded that the reduction of oxygen consumption in heat acclimation is due to the reduction of thyroid activity. The effect of heat acclimation is strik3 ing in high CHO feeding, while less remarkable in high fat feeding. These dietary effect on difference of metabolism in heat acclimation may be a factor initiating the difference of seasonal variation of basal metabolism between Japanese and Western people whose dietary composition is quite different.
4) By feeding the food containing 0.1% propyl-thiouracil to block the thyroxine formation, the effect of food composition upon the thyroid function did not disappear, while the effects were diminished by hypophysectomy. Thus T. S. H. seems to play a role in the mechanism of dietary effect.
5) From above experimental results, it may be concluded that the high fat diet accelerates the cold acclimation, while high CHO diet promotes the heat acclimation.
