Renal Vascular Response to Salt Restriction in Normal Man: Evidence Against Adrenergic Mediation

The role of the sympathetic nervous system in the renal vasoconstriction induced by sodium restriction has been assessed in normal man in balance on a 10-mEq sodium intake. Renal blood flow was measured with radioxenon injected into the renal artery. Phentolamine infused into the renal artery at rates of up to 3 mg/min did not increase net renal perfusion or alter its intrarenal pattern. That dose of phentolamine was at least 30 times the threshold for significant blockade of the renal vascular effects of a large dose of epinephrine injected intra-arterially. The results suggest strongly that neither circulating catecholamines nor the sympathetic nerves play a central role in the renal vascular response to salt restriction in normal man.