EXOCYTOTIC RELEASE OF CATECHOLAMINES AND DOPAMINE‐β‐HYDROXYLASE FROM THE PERFUSED ADRENAL GLAND OF THE RABBIT AND CAT

Abstract

Secretion of catecholamines (CA) and dopamines‐hydroxylase (DBH) activity from the perfused rabbit and cat adrenal gland was studied following stimulation by a number of substances, including the physiological transmitter, acetylcholine (ACh), added to the perfusion fluid. Stimulation caused a proportional secretion of DBH and CA from the untreated rabbit adrenal. The ratio of DBH/CA was 11.2 + 0.9 (mean + s.e.) which was close to that found in the crude granule fraction of the contralateral gland (11.4 ± 0.7). After treatment with insulin (40 u/kg) for 3 h or with reserpine (0.25 mg/kg) for 24 h, CA and DBH contents decreased in a parallel fashion in the granule fraction, thus resulting in a similar ratio of DBH/CA in the gland. The ratio in the effluents after stimulation was similar to that found in the untreated gland. Higher doses of reserpine (0.7 to 2.5 mg/kg) increased the ratio of DBH/CA in the granule fraction and was dependent on the doses employed. The ratio in the effluents from these glands after stimulation paralleled these increased values. Concomitant secretion of CA and DBH in response to stimulation was also observed in the perfused cat adrenal. However, the ratio of DBH/CA in the effluents tended to be lower than that found in the granule fraction. These results support the concept of exocytotic secretion of CA in the adrenal medulla. 1979 British Pharmacological Society