Effect of Extreme Cold Exposure on Adrenocortical Function in the Unanesthetized Dog

¹ From the Naval Medical Research Institute, National Naval Medical Center, Bethesda, Maryland

Unanesthetized dogs with polyethylene cannulas in the right lumboadrenal vein were subjected to environmental temperatures of –46 to –50°C for 2–28 hours and –75 to –79°C for 4–5 hours. Adrenal venous blood samples were collected prior to, and during the periods of cold exposure, and analyzed for 17-hydroxycorticosteroids. In both temperature ranges, a marked increase in adrenal steroid output occurred soon after the onset of exposure in the 10 dogs studied. In 9 of the 10 animals, this response persisted for 1–3 hours after which adrenal steroid secretion returned to control, pre-exposure levels, despite continued cold exposure. The intravenous administration of 40 iu of ACTH produced a subsequent increase in adrenal 17-hydroxycorticosteroid output. Healthy dogs exposed to temperatures of –47°C for 28 hours and –79°C for 5 hours did not become hypothermic.