CATECHOLAMINES AND DOPAMINE--HYDROXYLASE SECRETION FROM PERFUSED GOAT ADRENAL GLANDS

¹ Department of Pharmacology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060 Japan

Splanchnic nerve stimulation caused a frequency-dependent increase in catecholamine (CA) secretion which attained a maximum at 10 Hz in perfused goat adrenal glands. Acetylcholine (ACh) and nicotine also caused a dose-dependent increase in CA secretion. The percentage of three catecholamines released (adrenaline, 51-56%; noradrenaline, 42-47; dopamine, 1·3-2%) were not significantly different among three different stimuli. These values were almost the same as those found in the extract of adrenal gland and in purified chromaffin granules. The response to ACh was completely abolished by hexamethonium alone. Pilocarpine was ineffective in increasing CA secretion. Dopamine--hydroxylase (DBH) activity increased with the increase in CA secretion in response to splanchnic nerve stimulation and ACh, though the declining phase of DBH was much slower than that of CA. The ratios of CA to DBH activity released for 25 min during and after splanchnic nerve stimulation and ACh infusion were 0·40 ± 0·07 and 0·50 ± 0·07, respectively. The ratio was 0·41 ± 0·06 in chromaffin granules. The results indicate that only nicotinic receptors are involved in CA secretion and that DBH may be useful as an index of exocytosis in goat perfused adrenal glands.