Elsevier

Life Sciences

Volume 25, Issue 3, 16 July 1979, Pages 265-271
Life Sciences

Elevation of plasma tyrosine after a single oral dose of L-tyrosine

https://doi.org/10.1016/0024-3205(79)90294-7Get rights and content

Abstract

Plasma tyrosine concentrations in twelve normal, fasting human subjects were significantly elevated 2–8 hours after they ingested 100 mg/kg or 150 mg/kg tyrosine. Mean plasma tyrosine levels were maximal after 2 hours, rising from 69 ± 3.9 to 154 ± 9.5 nmols/ml(X ± SEM) after the 100 mg/kg dose and to 203 ± 31.5 nmols/ml after the 150 mg/kg dose (p ≤ 0.001 for both doses). The mean tyrosine ratio (defined as the ratio of plasma tyrosine concentration to the sum of the concentrations of six other neutral amino acids that compete for the same blood-brain barrier uptake system) increased from 0.10 ± 0.02 to 0.28 ± 0.04 (X ± SEM) 2 hours after the 100 mg/kg dose (p ≤ 0.001) and to 0.35 ± 0.05 2 hours after the 150 mg/kg dose (p ≤ 0.005). No side effects of orally-administered L-tyrosine were noted.

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These studies were supported in part by grants from the National Institutes of Health (AM-14228) and the National Aeronautics and Space Administration (NGR-22-009-627). Dr. Melamed is an NIH- Fogarty International Fellow (FO5 TW 02579-01). Dr. Growdon is the George Cotzias Fellow of the American Parkinson's Disease Association.

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