The effect of hypoxia on the levels of circulating catecholamines in the dogfishScyliorhinus canicula

Summary

• 1. A radio-enzymatic technique was used to assay the catecholamines, dopamine (DA), noradrenaline (NA) and adrenaline (A) in relatively small samples of dogfish blood, obtained from an indwelling cannula. The removal of a 2 ml sample of blood has no appreciable effect on the levels of circulating catecholamines in the dogfish. Thus, the three amines could be measured before and after a particular experimental treatment by removing 2 ml of blood before and 7–8 ml of blood after the treatment.

• 2. In resting, normoxic dogfish at 15°C, the mean (±S.E.) levels of the three amines in the plasma were: DA, 6.0±1.2 pmol ml⁻¹; A, 25.6±6.5 pmol ml⁻¹; NA, 32.1±19.3 pmol ml⁻¹. Following exposure to an inspired oxygen tension of approximately 35 mmHg for 1.5 h there was an increase in all three catecholamines to: DA, 11.3±1.4 pmol ml⁻¹; A, 284.4±86.2 pmol ml⁻¹; NA, 446.5±117.6 pmol ml⁻¹. These increases are discussed in terms of the known effects of the substances on the isolated heart and branchial arteries of elasmobranchs.