Influences of norepinephrine transporter function on the distribution of sympathetic activity in humans.
Previous studies suggest that neuronal norepinephrine transporter function may regulate the distribution of sympathetic activity among blood vessels, heart, and kidney; we tested the functional relevance in humans. Sixteen healthy men (26+/-1 years) ingested 8 mg of the selective norepinephrine reuptake transporter inhibitor reboxetine or a matching placebo on 2 separate days in a double-blind, randomized, crossover fashion. We monitored heart rate, thoracic bioimpedance, blood pressure, glomerular filtration rate, and renal blood flow. Ninety minutes after ingestion of the test medication, subjects were tilted to a 45 degrees head-up position, where they remained for an additional 30 minutes. Reboxetine increased supine systolic blood pressure through an increase in cardiac output whereas systemic vascular resistance decreased. Furthermore, reboxetine increased heart rate, particularly with a head-up tilt. Supine plasma renin activity was 0.71+/-0.15 ng angiotensin (Ang)/L per mL/h with placebo and 0.36+/-0.07 ngAng/L per mL/h with reboxetine (P<0.01). Supine plasma Ang II concentrations were also decreased with reboxetine. Both plasma renin activity and Ang II concentrations remained suppressed during head-up tilt. On placebo, renal vascular resistance increased with head-up tilt. The response was abolished with norepinephrine reuptake inhibition. We conclude that norepinephrine reuptake function profoundly influences the distribution of sympathetic activity between the heart, vasculature, and kidney in humans. All of these changes are physiologically relevant because they lead to corresponding changes in organ function.
Mayer
Antje F
AF
Franz-Volhard-Clinical Research Center, Medical Faculty of the Charité, Max-Delbrueck Centrum, and HELIOS Klinikum, Berlin, Germany.
Schroeder
Christoph
C
Heusser
Karsten
K
Tank
Jens
J
Diedrich
André
A
Schmieder
Roland E
RE
Luft
Friedrich C
FC
Jordan
Jens
J
D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology*; D000328:Adult; D000804:Angiotensin II / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011187:Posture; D000077593:Reboxetine; D012079:Renal Circulation / Q000187:drug effects; D012083:Renin / Q000097:blood; D013564:Sympathetic Nervous System / Q000187:drug effects*
D018759:Adrenergic Uptake Inhibitors; D009025:Morpholines; D050484:Norepinephrine Plasma Membrane Transport Proteins; D000804:Angiotensin II; D000077593:Reboxetine; D012083:Renin; D009638:Norepinephrine