BODY TEMPERATURE, THYROID AND ADRENAL CORTEX OF HAMSTERS DURING COLD EXPOSURE AND HIBERNATION, WITH COMPARISONS TO RATS1

Abstract

When compared with controls kept at 23[degree]C, non-hibernating Syrian hamsters exposed to air of 5[degree]C, or those in the hibernating state for 1 to 83 days, showed no enlargement of the adrenals, nor any histophysiological evidence of hyperactivity of either the zona fasciculata of the adrenal cortex or of the thyroid. However, enlargement and increased lipid content of the zona glomerulosa of the adrenal developed, and free lipid made its appearance in the shrunken zona reticularis. In contrast, rats exposed to identical cold environment showed histophysiological signs of increased activity of both glands. Rats maintained their body temperatures in the cold, with or without bedding, whereas hamsters displayed more stable body temperatures without bedding. Experimental treatments other than cold, however, induced typical endocrine responses in hamsters. Thiouracil administration caused enlargement of the thyroids; injections of epinephrine for 7 or 42 days produced some adrenal enlargement Hibernators contrasted with non-hibernators in that neither the pituitary-adrenal or pituitary-thyroid axis seemed stimulated by moderate cold. Adrenals of hibernators seemed to alter principally with respect to sexual activity; further, the adrenals of hibernators were remarkably lipid-poor. It was concluded that polyglandular insensitivity of the endocrines to cold was typical of hibernators but was not a causative factor in the process of entering hibernation.