Abolition, by dopamine blockade, of the natriuretic response produced by lower-body positive pressure.
1. In a preliminary study, a positive pressure of 25 mmHg applied to the lower body raised right atrial pressure by a mean of 7 mmHg. 2. Sustained application of lower-body positive pressure (LBPP) in six normal adult males increased sodium excretion ([Na]V) from a control level of 126.5 +/- 10 mumol/min to 213 +/- 21 mumol/min (P = 0.003) and fractional sodium excretion (EfNa) from 0.7 +/- 0.1 to 1.2 +/- 0.1 (P = 0.001). 3. Urine flow (UF) increased from 0.85 +/- 0.07 ml/min to 4.1 +/- 0.8 ml/min (P = 0.002), osmolar clearance (Cosm) from 2.6 +/- 0.13 ml/min to 4.2 +/- 0.4 ml/min (P = 0.003) and free water clearance (CH2O) from -1.75 +/- 0.1 ml/min to -0.1 +/- 0.01 ml/min (P = 0.001). Creatinine clearance (Ccr) showed no significant change. 4. After dopamine blockade with domperidone, LBPP did not cause a rise in [Na]V or EfNa. However, urine flow, Cosm. and CH2O remained significantly above control values, implying persistent suppression of antidiuretic hormone. 5. Dopamine blockade without positive pressure did not affect basal sodium excretion.
D000293:Adolescent; D000328:Adult; D000399:Air Pressure; D001274:Atmospheric Pressure; D001794:Blood Pressure; D004231:Diuresis / Q000187:drug effects; D004294:Domperidone / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology*; D006321:Heart / Q000502:physiology; D006801:Humans; D008297:Male; D009318:Natriuresis / Q000187:drug effects*; D012964:Sodium / Q000652:urine
D004294:Domperidone; D012964:Sodium; D004298:Dopamine