A STUDY OF THE CELLULAR SITE OF CATECHOLAMINE RELEASED BY CARBACHOL STIMULATION OF THE ADRENAL MEDULLA

¹ Department of Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York

A study was conducted of the cellular site of catecholamines released by carbachol stimulation of the adrenal medulla using isolated perfused cat adrenals. In these studies employing tritiumlabeled epinephrine (E), it was ascertained that the specific activity of E (counts per minute per microgram) released into the effluent of the perfused gland after carbachol stimulation was significantly different from time specific activity of E in the granular fraction which was isolated from the gland and analyzed immediately after stimulation. Further, the specific activity of E released on stimulation was not significantly different from that found in the isolated extragranular fraction. Three possible interpretations of the results are that the catecholamine released comes 1) from a nongranular (cytoplasmic) pool; 2) from special granules which have a specific activity which is higher than the average for all granules and is the same as that of the nongranular pool; and 3) from special granules which have a higher specific activity than the average for those chromaffin granules which survive isolation, and which in large part do not survive isolation themselves but actually lose their catecholamine to the nongranular fraction during isolation.