SKELETAL MUSCLE: RESERVOIR FOR EXOGENOUS L-DOPA

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 190; no. 1; pp. 187 - 191
• Main Authors: Ordonez, L A, Arbrus, M, Boyson, S, Goodman, M N, Ruderman, N B, Wurtman, R J
• Format: Journal Article
• Language: English
• Published: United States American Society for Pharmacology and Experimental Therapeutics 01.07.1974
• Subjects: Animals; Brain Chemistry - drug effects; Dietary Carbohydrates - pharmacology; Dihydroxyphenylalanine - blood; Dihydroxyphenylalanine - metabolism; Dihydroxyphenylalanine - pharmacology; Fats - pharmacology; Hindlimb - metabolism; Insulin - pharmacology; Male; Muscles - metabolism; Perfusion; Rats; Spectrometry, Fluorescence; Time Factors; Tritium
• ISSN: 0022-3565; 1521-0103

In previous studies it has been shown that skeletal muscle concentrates exogenous L -dopa from the blood more effectively than most other tissues. The present study further examines the metabolism of L -dopa in muscle. At all times studied after L -dopa administration to rats, the concentrations of the drug were higher in muscle than in serum or brain. The total amounts of unmetabolized dopa present in muscle were increased by prior insulin administration or carbohydrate consumption; these treatments also increased brain dopa. Of the dopa-derived molecules present in various tissues after administration of the amino acid, muscle contained the largest unmetabolized fraction. This finding is compatible with in vitro evidence that muscle contains little catechol-O-methyltransferase or dopa decarboxylase activity and suggests that muscle does not metabolize dopa to a significant degree. Isolated perfused hindquarters taken from rats pretreated with L -dopa released the unmetabolized amino acid into the perfusate; this suggests that when L -dopa concentrations in skeletal muscle exceed those of serum, dopa may also be released into the circulation in vivo.