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Differences in the neuronal removal of circulating epinephrine and norepinephrine
G Eisenhofer1, M D Esler, H S Cox
1Baker Medical Research Institute, Prahran, Victoria, Australia.
The Journal of Clinical Endocrinology and Metabolism
|June 1, 1990
Summary
Epinephrine is removed less effectively by sympathetic neurons than norepinephrine. This study found neuronal uptake and metabolism significantly lower for epinephrine, impacting its clearance.
Area of Science:
- Pharmacology
- Neuroscience
- Cardiovascular Research
Background:
- Neuronal uptake is key for norepinephrine removal.
- The role of neuronal uptake in epinephrine removal is not well understood.
Purpose of the Study:
- To compare the neuronal removal of epinephrine and norepinephrine.
- To investigate the contribution of neuronal uptake to epinephrine clearance.
Main Methods:
- Examined cardiac extractions and plasma clearances of radiolabeled epinephrine and norepinephrine in healthy subjects, patients with cardiovascular disorders, and after desipramine administration.
- Utilized rabbit models to compare plasma clearances and dihydroxyphenylglycol (DHPG) formation.
Main Results:
- Cardiac extraction of epinephrine was significantly lower than norepinephrine in all groups.
- Desipramine (a neuronal uptake inhibitor) reduced epinephrine clearance less than norepinephrine clearance.
- Epinephrine showed 44-64% less avid neuronal uptake and metabolism compared to norepinephrine.
Conclusions:
- Sympathetic neuronal uptake and metabolism play a lesser role in epinephrine removal than in norepinephrine removal.
- Epinephrine clearance is less dependent on neuronal mechanisms compared to norepinephrine.