SKELETAL MUSCLE: RESERVOIR FOR EXOGENOUS L-DOPA

¹ Massachusetts Institute of Technology, Department of Nutrition and Food Science, Cambridge, Massachusetts

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.

This article has been cited by other articles:

				P. T. Mannisto and S. Kaakkola Catechol-O-methyltransferase (COMT): Biochemistry, Molecular Biology, Pharmacology, and Clinical Efficacy of the New Selective COMT Inhibitors Pharmacol. Rev., December 1, 1999; 51(4): 593 - 628. [Abstract] [Full Text] [PDF]