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Amethocaine‐induced inhibition of mitochondrial monoamine oxidase activity
Published in -
Volume: 38
Issue: 11
Pages: 858 - 860
Amethocaine (tetracaine) (1–10 μM) produces a concentration‐dependent in‐vitro inhibition of mitochondrial membrane‐bound MAO activity towards tyramine (18–84% in brain and 19–84% in liver) and 5‐hydroxytryptamine (5‐HT) (23–94% in brain and 20–100% in liver). At relatively higher concentrations (25–300 μM) of amethocaine, benzylamine oxidation is inhibited in brain (24–91%) and liver (29–100%). The extent of MAO inhibition is appreciably reduced when preincubation time of the enzyme with a low concentration (7.5 μM) of amethocaine is increased from zero to 45 min. This inhibition is reversible. The Km of MAO for tyramine is increased in brain (106–473%) and liver (121–352%) in the presence of amethocaine (2–7.5 μM) accompanied by a decrease in Vmax (21–51% in brain and 18–57% in liver). Similarly the Km of MAO for 5‐HT is increased to the extent of 79–336% in brain and 51–225% in liver and the corresponding Vmax is decreased by 35–55% and 39–74%, respectively, in the presence of 2–5 μM amethocaine. At relatively higher concentrations (25–100 μM), amethocaine increases the Km of MAO for benzylamine in brain (25–101%) and liver (26–85%) and decreases the Vmax by 28–64% and 32–63% in the respective tissues. Thus these results suggest that amethocaine preferentially inhibits MAO‐A and the nature of inhibition is reversible and of mixed type. Copyright © 1986, Wiley Blackwell. All rights reserved
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JournalJournal of Pharmacy and Pharmacology