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Dopamine and its metabolites in human tears
1Department of Ophthalmology, University of Zurich, Switzerland.
European Journal of Ophthalmology
|April 1, 1993
Summary
Tears contain dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). This suggests a potential role for tear dopamine in corneal ion transport and lacrimal gland function.
Area of Science:
- Ophthalmology
- Neurochemistry
- Tear Film Physiology
Background:
- Dopamine is recognized for stimulating ion transport in the corneal epithelium.
- The corneal epithelium's direct contact with the tear film necessitates investigation into tear composition.
Purpose of the Study:
- To detect and quantify dopamine and its primary metabolites in human tears.
- To explore the potential source and metabolic pathways of dopamine in the ocular environment.
Main Methods:
- Tear samples (20 microliters) were collected from 20 healthy subjects following trigeminal stimulation.
- High-performance liquid chromatography with electrochemical detection was employed for precise analysis.
Main Results:
- Dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) were identified and measured in tears.
- Mean concentrations were: dopamine (8.9 ± 5.1 ng/ml), DOPAC (2.2 ± 1.6 ng/ml), and HVA (0.55 ± 0.4 ng/ml).
Conclusions:
- The presence of dopamine and its metabolites suggests enzymatic activity within the lacrimal system.
- Dopamine catabolism likely involves monoamine oxidase and catechol-O-methyltransferase, occurring in the lacrimal gland and possibly corneal epithelium.
- Tear-derived dopamine may contribute to the regulation of corneal ion transport.