Thyroxine and norepinephrine effects on the metabolic rates of heat-acclimated hamsters.

Metabolic rates of heat-acclimated hamsters are lower than rates of controls when measured at ambient temperatures of 32 C and –15 C. Separate administration of norepinephrine or thyroxine decreases the difference between the 2 groups, while their combined administration eliminates the difference entirelywhen metabolic rates are measured at ambient temperatures of 32 C. Administration of these hormones separately or together does not affect the metabolic rates of the control groups, but slightly stimulates those of the heatacclimated hamsters, when measured at –15 C. (Endocrinology 82:17,1968)