Adrenal Medullary Secretion During Hypoxia, Bleeding, and Rapid Intravenous Infusion

Abstract

This study reports the effect of hypoxia, of lowering blood pressure by bleeding, and of rapid infusion upon adrenal secretion in anesthetized dogs. Adrenal norepinephrine-like substances (NEL) were measured in adrenal venous blood by means of a bio-assay method, using the rabbit aortic strip. In 10 of 11 dogs breathing 7.1 per cent O₂ in N₂, the left adrenal NEL output was augmented 1.5 to 6.6 times control levels. The increased adrenal medullary secretion during hypoxia was not dependent upon a fall in systemic arterial blood pressure and was not associated with an increase of 17-hydroxycorticosteroid output. In five dogs bled to a blood pressure of 80 to 90 mm. Hg, left adrenal NEL output was augmented 2.9 to 7.4 times control levels. In 11 animals in which the blood pressure was lowered to 40 to 50 mm. Hg by bleeding, left adrenal NEL output was augmented 1.8 to 17 times control levels. Seven dogs were made anemic and hypervolemic by rapid infusion of 1,125 to 1,900 ml. normal saline or Krebs' solution. Cardiac outputs were increased more than 200 per cent in six, and considerable dilution anemia was produced. However, left adrenal NEL outputs fell to values ranging from 14 to 50 per cent of control. During rapid infusions, output of adrenal 17-OHCS increased 18.5 to 92 per cent. It is concluded that increased adrenal medullary secretion did not participate in the increase of cardiac output observed in these seven animals.