1. In chloralose-anaesthetized dogs, central venous and arterial angiotensin (AII) levels were monitored by blood-bathed bioassay during venous haemorrhage of 20 ml/kg, acute renal ischaemia induced by suprarenal aortic stenosis and frusemide-induced diuresis.
2. Blockade of intrarenal dopamine receptors with ergometrine reduced markedly the increments in arterial AII associated with haemorrhage or suprarenal aortic stenosis, but did not consistently affect the corresponding increments in venous AII.
3. Ergometrine or renal denervation did not affect the increases of blood AII associated with frusemide diuresis.
4. Blockade of β-adrenoreceptors with propranolol, by contrast, reduced blood AII increments associated with all three procedures.
5. It is suggested that renin release during moderate haemorrhage and acute suprarenal aortic stenosis is, in the dog, partly due to activation of intrarenal dopaminergic nerves.
6. The possibility is discussed that propranolol may depress renin release in the dog by an action other than that of blocking β-adrenoreceptors.