The effects of bradykinin, angiotensin and acetylcholine on the bovine adrenal medulla.

1. The response of the adrenal medulla to the intra-arterial injection of angiotensin, bradykinin and acetylcholine and to splanchnic nerve stimulation has been investigated in day-old and 3- to 18-month-old calves and in adult cats.2. Bradykinin and angiotensin had no appreciable effect on catecholamine release in the day-old calf nor did these peptides potentiate the response of the gland to acetylcholine.3. In older calves the response of the gland to bradykinin and angiotensin was marginally above the control output, whereas acetylcholine and splanchnic nerve stimulation caused a 10-100 fold increase in the rate of secretion. The response to acetylcholine but not to the peptides was related to the dose administered.4. The adrenal medulla of the cat was stimulated by angiotensin and bradykinin but the maximum amounts released by the peptides were much smaller than the discharge elicited either by splanchnic nerve stimulation or by acetylcholine. No dose-response relationship could be found for either adrenaline or noradrenaline released by angiotensin, or for noradrenaline released by bradykinin. The slight increase in adrenaline output which followed the injection of bradykinin was dependent on the dose but the slope of the curve (b = 0.161) was much less than that for acetylcholine (b = 0.636).