Exocytotic release of catecholamines and dopamine-beta-hydroxylase from the perfused adrenal gland of the rabbit and cat.

1 Secretion of catecholamines (CA) and dopamine-beta-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. 2 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). 3 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. 4 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. 5 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. 6 These results support the concept of exocytotic secretion of CA in the adrenal medulla.