Dopamine-β-hydroxylase activity in the axillary bodies, the heart and the splanchnic nerve in two elasmobranchs, Squalus acanthias and etmopterus spinax

Abstract

1. The activity of dopamine-β-hydroxylase (DBH) was examined in tissues from Squalus acanthias and Etmopterus spinax using tyramine as substrate. 2. The activity of DBH in axillary bodies in Squalus was 19040 ± 240 nmol/g per hr and in Etmopeterus 6120 ± 245 nmol/g per hr. 3. DBH activity in nervous tissue, i.e. the splanchnic nerve (together with coeliac artery) was found to be 123 ± 41 nmol/g per hr in Squalus and 384 ± 62 nmol/g per hr in Etmopterus. 4. In Squalus heart DBH activity was undetectable, while Etmopterus heart had DBH activity both in atrium and ventricle, 40 ± 13 and 18 ± nmol/g per hr respectively. 5. A small amount of DBH activity was found in Squalus blood plasma, 2 ± 0.7 nmol/ml per hr. 6. The DBH activity gave high formation of octopamine in a wide temperature range from 24.5 to 32°C.