Renin-angiotensin mediation of adrenal catecholamine secretion induced by haemorrhage.

The mechanism involved in catecholamine (CA) release from cat adrenal gland, in response to haemorrhage was studied. In intact cats, in cats with bilateral cervical vagotomy or following bilateral ureteral ligation, haemorrhage induced an increased catecholamine release from the adrenal (with increased percentage of noradrenaline). Acute bilateral nephrectomy, chronic sodium loading with repeated administration of desoxycorticosterone acetate (DOCA), or acute denervation of the adrenal gland, completely abolished the increased CA release from the adrenal gland following haemorrhage. Haemorrhage induced an increase of plasma renin concentration in intact cats and after ureteral ligation but there was no increase in plasma renin after haemorrhage in cats with bilateral nephrectomy or following pretreatment with DOCA and salt load. Following haemorrhage in intact cats, blood pressure showed an immediate fall followed by rapid recovery. The recovery of blood pressure after haemorrhage was abolished in cats with bilateral nephrectomy. It is concluded that the adreno-medullary response to haemorrhage in the cat, depends primarily on the intact renal renin angiotensin system. Angiotensin, generated peripherally, probably affects the CNS and activates the sympathetic nerves.