It has previously been shown that the blood pyruvate and lactate decrease slightly in hot environmental conditions, but changes of intermediates of Krebs' cycle, which included from citric acid to oxaloacetate, have not yet been reported. On the other hand, the serum calcium, which formed a soluble complex with the serum citric acid, increased slightly due to exposure to heat.
From these results we can assume that serum citrate decreases according to the fall of pyruvate, while it increases slightly in proportion to the rise of serumm calcium. It seems of interest, therefore, to ascertain whether the serum citrate would increase or decrease in high temperature environment.
During mid winter, I had 4 healthy young men lie quietly on the beds in the ordinary room temperature of 29°C, and subsequently for 180 minutes in the hot chamber of 30°C, 34°C and 37°C, or for 90 minutes when the air temperature was as high as 40°C and 44°C. Bloods were withdrawn just before the subjects were leaving the ordinary temperature room or hot chamber.
In the case of rest in the ordinary temperature room, serum citrates decreased slightly in a process of times, but this change was also seen after a stay in the hot chamber. Consequently, it seems to me that heat exposure can exert little effect on the serum citrate.
View full abstract