Central role for angiotensin in control of adrenal catecholamine secretion

Angiotensin II (ANG II) is required for unimpaired adrenal reflex secretion of catecholamines after hemorrhage in the dog. To test if ANG II acts centrally, experiments were performed under general anesthesia on bilaterally or sham-nephrectomized dogs hemorrhaged at 25 ml/kg. Ventriculocisternal perfusion of ANG II or its antagonist saralasin was accomplished via needles inserted in the left lateral cerebral ventricle and cisterna magna. Mean arterial pressure and adrenal secretion of catecholamines were measured before and after hemorrhage. Nephrectomized dogs receiving only artificial cerebrospinal fluid (CSF) by ventriculocisternal perfusion had a very small adrenal response to hemorrhage compared with animals receiving ANG II intraventricularly (IVT) (at 10 and 100 pg . kg-1 . min-1). This effect of ANG II IVT also depended on the rate of IVT infusion. Peripheral infusion of ANG II (10 pg . kg-1 . min-1) had no effect on adrenal catecholamine secretion. Animals with intact kidneys given saralasin IVT (0.06 ng/min) responded similarly to nephrectomized dogs receiving only CSF IVT. Intravenous saralasin did not blunt the response to hemorrhage. Thus ANG II appears to support catecholamine secretion via a central mechanism. This mechanism is physiologically significant because either nephrectomy or functional elimination of ANG II by saralasin greatly attenuates the adrenal medullary response to hemorrhage in vivo.