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Regional 5-hydroxyindoleacetic acid production in humans
G W Lambert1, D M Kaye, H S Cox
1Human Autonomic Function Laboratory, Baker Medical Research Institute, Prahran Victoria, Australia.
Life Sciences
|January 1, 1995
Summary
The gut is the primary source of 5-hydroxyindoleacetic acid (5-HIAA) in circulation, with production influenced by organ contributions and clearance rates. Sympathetic nervous system activity impacts 5-HIAA levels, highlighting its complex regulation.
Area of Science:
- Pharmacology and Physiology
- Metabolic Biochemistry
- Neuroendocrinology
Background:
- 5-hydroxyindoleacetic acid (5-HIAA) is a key metabolite of serotonin, a crucial neurotransmitter and hormone.
- Understanding the origins and regulation of peripheral 5-HIAA is essential for interpreting its role in physiological and pathological states.
- Previous studies have not fully elucidated the quantitative contributions of various organs to circulating 5-HIAA or the influence of autonomic function.
Purpose of the Study:
- To quantify the regional organ contributions to peripheral plasma 5-hydroxyindoleacetic acid (5-HIAA) levels.
- To investigate the role of the kidneys in 5-HIAA clearance.
- To explore the relationship between sympathetic nervous system activity and 5-HIAA production and concentration in healthy individuals and patient cohorts.
Main Methods:
- Measurement of veno-arterial plasma concentration differences and regional organ plasma flows in healthy subjects.
- Assessment of 5-HIAA extraction by the renal circulation.
- Analysis of plasma 5-HIAA concentrations and production/clearance rates in patients with chronic heart failure and autonomic failure.
Main Results:
- The hepatosplanchnic organs, particularly the gut, are the largest contributors (58%) to the total plasma 5-HIAA pool, followed by skeletal muscle (26%).
- The renal circulation is the primary site for 5-HIAA clearance, extracting 18 +/- 2 nmol/min.
- Elevated plasma 5-HIAA in heart failure patients was linked to increased production, while in autonomic failure patients, it was due to reduced clearance; hepatic vein 5-HIAA correlated with sympathetic activity in healthy subjects.
Conclusions:
- Peripheral 5-HIAA plasma concentration is determined by a balance between production from multiple body sites and clearance, predominantly by the kidneys.
- The gut is the major source of circulating 5-HIAA, with minimal contribution from the brain.
- Sympathetic nervous system activity influences 5-HIAA overflow into the circulation, suggesting a link between autonomic function and serotonin metabolism.