A STUDY OF THE DIFFERENTIAL SECRETION OF EPINEPHRINE AND NOREPINEPHRINE FROM THE PERFUSED CAT ADRENAL GLAND

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

Experiments were carried out on cat adrenal glands perfused with Locke's solution to study the differential release of epinephrine (E) and norepinephrine (NE) under different conditions of stimulation and inhibition. The addition of KCl to the perfusion medium in the concentration range of 17 to 84 mM for 2-min periods caused a graded increase in the rate of total catecholamine secretion. Over the concentration range 5.6 to 28 mM KC1, NE accounted for only 30% of the total catecholamine secreted. Raising the K⁺ concentration to 56 mM increased the percent NE to 61%. Prolonged stimulation with 17 mM KCl did not significantly alter the NE/E ratio; however, during the 2- to 6-min period of stimulation with 28 mM KC1, the percent NE increased to 65%. Low concentrations of nicotine released a predominance of NE, equipotent concentrations of piocarpine (in terms of total catecholamine output) released a predominance of E and acetylcholine released approximately equal amounts of E and NE. Tetracaine inhibited preferentially the NE-dominant secretion induced by nicotine. Only in high concentrations did tetracaine depress the catecholamine secretion elicited by agents which released a predominance of E. These results are discussed in relation to the possible existence of two types of medullary chromaffin cells, which contain either E or NE and possess certain pharmacologically distinguishable characteristics.