Abstract
Renal and total dopamine (DA) spillover rates at rest were measured in 25 conscious rabbits with chronically implanted renal vein catheters. Renal DA spillover rate was calculated from veno-arterial difference in plasma free DA concentrations across the kidney corrected by the fractional extraction of infused 3H-DA. Plasma free DA concentrations were 11.0±2.7pg/ml in the artery and 14.3±3.6 in the renal vein. Renal and total DA spillover rates were 0.51±0.08, 2.61±0.30ng/min, respectively, both of which were significantly (p<0.001) lower than the respective norepinephrine (NE) spillover rates (renal: 16.3±1.4, total: 39.6±1.7). The fractional extraction of 3H-DA across the kidney (55±3%) and the total DA clearance (285±31ml/min) were both significantly (p<0.05) higher than that of 3H-NE (45±3) and the total NE clearance (198±9), respectively. The ratio of renal to the total spillover rate of DA 0.23±0.05) was significantly (p<0.05) lower than that of NE (0.41±0.04). These results demonstrate that DA is released into plasma within the kidney and suggest that the measurement of renal DA spillover rate using 3H-DA radiotracer technique is useful to detect resting reenal dopaminergic nerve activity. (Hypertens Res 1995; 18 Suppl. I: S145-S146)
