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Skin color, aging, and plasma L-dopa levels
1Intramural Research Program, National Institute of Neurological and Communicative Diseases and Stroke, Bethesda MD 20892.
Journal of the Autonomic Nervous System
|April 1, 1989
Summary
Skin pigmentation does not significantly impact circulating L-dopa levels. However, L-dopa levels decrease with age, while norepinephrine levels increase, altering their ratio in aging individuals.
Area of Science:
- Biochemistry
- Human Physiology
- Dermatology
Background:
- Plasma L-dopa is primarily from catecholamine tissues.
- Melanocytes produce L-dopa during melanin synthesis.
- The contribution of melanocytes to circulating L-dopa is uncertain.
Purpose of the Study:
- To investigate the role of skin pigmentation in plasma L-dopa levels.
- To examine age-related changes in plasma L-dopa and norepinephrine.
- To determine the L-dopa:norepinephrine ratio in different age groups.
Main Methods:
- Compared plasma L-dopa in albino, Caucasian, and Black volunteers.
- Included patients with essential hypertension.
- Correlated L-dopa and norepinephrine levels with age in Caucasian volunteers.
Main Results:
- Plasma L-dopa levels were similar across all subject groups.
- Skin pigmentation did not significantly affect plasma L-dopa.
- L-dopa levels negatively correlated with age (r = -0.30, P < 0.05).
- Norepinephrine levels showed a trend of increasing with age (r = 0.25, 0.05 < P < 0.10).
- The L-dopa:norepinephrine ratio strongly negatively correlated with age (r = -0.50, P < 0.01).
Conclusions:
- Human skin pigmentation is not a major contributor to plasma L-dopa.
- Plasma L-dopa levels decrease with normal aging.
- The L-dopa to norepinephrine ratio declines significantly with age.