THE EFFECT OF HYPOTHERMIA ON PITUITARY AGTH 



RELEASE AND ON ADRENAL CORTICAL AND 



MEDULLARY SECRETION IN THE DOG* 



D. M. HUME, R. H. EGDAHLf and D. H. NELSON 



Some studies on adrenal cortical function in hypothermia are available in the 

 literature. Khalil/ using adrenal ascorbic acid depletion, reported that the adrenal 

 was responsive to ACTH stimulation during hypothermia, although the response 

 was greatly decreased. Egdahl et air' ^ found that adrenal venous blood 17-hydroxy- 

 corticosteroid secretion was markedly reduced in hypothermia, and similar results 

 were obtained by Ganong et al.^ 



The present brief report concerns work done by our group on blood ACTH 

 levels, adrenal corticosteroid secretion, and epinephrine and norepinephrine output 

 in hypothermia. Most of this work has been or will be reported in more detail 

 elsewhere. 



Methods. The hypothermia studies were carried out, for the most part, as acute 

 experiments on dogs which were traumatized under ether anesthesia and then 

 cooled. Adrenal venous blood samples were obtained by the method of Hume and 

 Nelson.** This consisted of placing a cannula in the lateral aspect of the lumbo- 

 adrenal vein and briefly occluding the adrenal vein at its junction with the vena 

 cava. A polyethylene snare was used so that intermittent occlusion of the vein 

 could be produced externally whenever it was desired to obtain a sample. During 

 the periods of occlusion all of the adrenal blood flowed out the cannula and was 

 collected in graduated centrifuge tubes. The adrenal venous blood was assayed for 

 17-hydroxycorticosteroid content by the method of Nelson and Samuels." 



Arterial blood ACTH content was determined by the method of Nelson and 

 Hume." In this technique the corticosteroidogenic capacity of the peripheral blood 

 ACTH is tested in the hypophysectomized dog. The blood ACTH was determined 

 before the induction of hypothermia, during hypothermia, and after rewarming. 



Adrenal venous blood epinephrine and norepinephrine levels were measured by 

 the method of Aronow.^ 



Hypothermia was induced by ice water immersion, air cooling, or by cooling an 

 external vascular shunt. The animals were cooled to 21°-28° C. Some of the ani- 

 mals received a constant intravenous drip of ACTH at a rate of 80 milliunits per 

 minute during the production of hypothermia. In some experiments the adrenal 

 was cooled locally while the animal remained normothermic, and in others the ani- 

 mals were allowed to become hypothermic while the systemic blood pressure was 

 maintained with a continuous infusion of norepinephrine. Adrenal function was 

 also assessed in normothermic unanesthetized dogs exposed to cold at — 10° C, 

 — 48° C. and —78° C. In these dogs the adrenal cannula was placed under sterile 



* From the Surgical Research Laboratory, Harvard Medical School, Boston, Massachusetts, 

 and the Naval Medical Research Institute, Rethesda, Maryland. The opinions or assertions con- 

 tained herein are those of the writers and are not to he construed as official or reflecting the 

 views of the Navy Department or the Naval Service at large. 



t Present address: University Hospitals, Minneapolis 14, Minnesota. 



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