Li Kam Wa TC, Freestone S, Samson RR, Johnston NR, Lee MR. The antinatriuretic action of gamma-L-glutamyl-5-hydroxy-L-tryptophan is dependent on its decarboxylation to 5-hydroxytryptamine in normal man.
Br J Clin Pharmacol 1994;
38:265-9. [PMID:
7826829 PMCID:
PMC1364799 DOI:
10.1111/j.1365-2125.1994.tb04351.x]
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Abstract
1. The effects of inhibition of peripheral aromatic L-amino acid decarboxylase during infusion of the relatively renally selective 5-hydroxytryptamine (5-HT) prodrug, gamma-L-glutamyl-5-hydroxy-L-tryptophan (glu-5-HTP), were examined in eight healthy male subjects in a randomised, placebo-controlled, cross-over study. 2. Each subject received oral carbidopa (100 mg) or placebo followed, 1 h later, by a 60 min intravenous infusion of glu-5-HTP (16.6 micrograms kg-1 min-1) or placebo. 3. After administration of glu-5-HTP, cumulative urinary excretion of 5-HT was 430-fold greater than that after placebo, and was associated with a period of sodium retention. 4. Pretreatment with carbidopa substantially attenuated the increase in 5-HT excretion after glu-5-HTP and abolished its antinatriuretic effect. 5. These results are in keeping with the proposition that the antinatriuretic action of glu-5-HTP is dependent on its decarboxylation to 5-HT.
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