THE MODE OF SECRETION OF CATECHOLAMINES FROM THE ADRENAL MEDULLA

¹ The Department of Pharmacology, Harvard Medical School, Boston, Massachusetts

The possibility that the heavy storage granules represent the sole immediate source of the catecholamines which are secreted by the adrenal medulla was tested in vivo.

Rats were treated with tritiated dopa of high specific activity so that labeled catecholamines were made and stored in the adrenal glands. The specific activity of the stored hormones was found to be the same as the specific activity of the hormones secreted into the adrenal vein. This finding supports the proposal that a degranulation mechanism operates and vitiates the proposition that a small but dynamic extragranular pool shunts freshly formed catecholamines past the granules directly into the blood.

In the rat anesthetized with pentobarbital and subjected to laparotomy, the biological half-life of the catecholamines in the adrenal gland is 1 day, while others have found that under experimental conditions which involved no anesthesia or surgery, the half-life is 10 days.