Angiotensin II Restoration of Reflex Adrenal Medullary Secretion to Anephric Dogs Is Physiologically Dose Dependent*

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Abstract
Acute nephrectomy seriously impairs hypovolemic adrenal epinephrine (E) release in the anesthetized dog. That systemically delivered angiotensin II totally restores E release to acutely anephric dogs is equally clear, but the dose-response relationship of this angiotensin II effect is not known. Adrenal secretion rates and arterial plasma E, norepinephrine (NE), and dopamine levels were studied in nine groups of mongrel dogs (n = 5 in each group) under pentobarbital anesthesia: 1) resting animals; 2) hemorrhage (25 ml/kg); 3) hemorrhage after acute nephrectomy; 4-7) hemorrhage, acute nephrectomy, plus iv angiotensin II at a) 0.01 ng/kg .cntdot. min, b) 0.10 ng/kg .cntdot. min, c) 1.00 ng/kg .cntdot. min, or d) 10.00 ng/kg \ min; 8) no hemorrhage, acute nephrectomy angiotension II (10.00 ng/kg .cntdot. min); and 9) hemorrhage, kidneys intact, iv angiotensin II (10.00 ng/kg .cntdot. min). Arterial and adrenal blood were sampled during a baseline prehemorrhage period and 15, 30, 60, and 90 min after hemorrhage. We confirm blunting of reflex E release by acute nephrectomy in the anesthetized dog and show that agniotensin II restores E (P < 0.01), NE (P < 0.01), and dopamine (P < 0.01) release in acutely anephric dogs. Aortic plasma E and NE were also restored to normal by angiotensin II (P < 0.01 for each). Dogs with intact kidneys show a blunted hemorrhage response of arterial plasma E (P < 0.01), NE (P < 0.01), and DM (P < 0.05) to our largest angiotensin II infusion rate (10 ng/lg .cntdot. min). The study demonstrates that in acutely anephric conditions, angiotensin II support of reflex catecholamine release is sensitively dose dependent to physiological infusion rates of systemic angiotensin II and suggests further that this angiotensin II effect is restrained by the kidneys.