Adaptation to Changes in Environmental Humidity at Constant Temperatures

Abstract

Summary(1) Rats acclimatized to a certain environmentaI temperature and relative humidity (10%-20% and 80%-100% respectively), were transferred to cages with a lower or higher humidity respectively, the temperature remaining constant at 28°-30°C. After transfer from “humid” to “dry” the daily output of urine and Cl and N excretion decreased during the first few days in about 50% of the experiments. On the other hand, transfer from “dry” to “humid” was followed in 80% of the experiments by a marked increase in urine output and Cl and N excretion. This effect also lasted only a few days. (2) Thyroidectomized rats did not show the reaction appearing in normal rats after transfer from “dry” to “humid” conditions. (3) It is, therefore, concluded that, with the temperature constant, changing the environmental humidity from “dry” to “humid” activates the thyroid gland. This activation represents an adaptive reaction of the body to the sudden change in the surrounding humidity.