Changes in cardiovascular and renal function during catecholamine infusions in developing swine.

Renal and cardiac effects of norepinephrine and dopamine were evaluated in swine aged 1 wk, 2 wk, and 6 mo. The swine were anesthetized with pentobarbital (20-30 mg/kg). Aortic pressure, right ventricular pressure and its first derivative, and heart rate were recorded, together with carotid and renal (RBF) arterial flows. Glomerular filtration rate (GFR) was determined by [14C]inulin clearance. After a control period, norepinephrine or dopamine was infused intravenously for 10-20 min before and then during another clearance period. After a second control period, the second catecholamine was infused. GFR increased in piglets given either catecholamine. Norepinephrine at equipressor doses (2.0 micrograms.kg-1.min-1 in piglets and 1.0 micrograms.kg-1.min-1 in mature swine) decreased RBF and increased renal resistance. Dopamine at equi-inotropic doses (10 micrograms.kg-1 min-1 in piglets and 20 micrograms.kg-1.min-1 in mature swine) increased RBF and decreased renal resistance only in mature swine. Infusions of dopamine at a low dose (5 micrograms.kg-1.min-1) also failed to increase RBF or decrease renal resistance in piglets. The results suggest that maturation of the mechanism of renal vasodilation by dopamine occurs later than that for vasoconstriction by norepinephrine.