Circulating catecholamines in control of renal electrolyte and water excretion

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Abstract
Graded physiological doses of norepinephrine [NE] or epinephrine [E] were infused either i.v. or directly into the renal artery of conscious dogs previously prepared with chronic indwelling catheters. Infusion rates ranged 5-125 ng .cntdot. kg-1 .cntdot. min-1, and aortic plasma catecholamine concentrations were measured during i.v. infusion to determine the actual levels achieved. Even when the renal arterial plasma NE concentration was raised to 5000 pg/ml by either i.v. or intrarenal infusion, only a modest Na and K retention was observed. Only i.v. NE increased urinary flow rate. Increments of E concentration from 120-2000 pg/ml decreased Na and K excretion only when delivered i.v. The concentrations of NE or E required to alter urinary Na and K excretion and flow rate were in the upper physiological range or higher and the responses were small except for i.v. E, which decreased Na excretion at very low physiological concentrations (120-400 pg/ml). Circulating E may play an important physiological role in renal Na conservation. This effect of E is not due to a direct intrarenal mechanism.