Abstract
The role of the intestine in metabolic inactivation of tyramine (TYR) has been studied in an isolated intestinal loop preparation in anaesthetized dogs. In control animals there was extensive metabolism of tyramine on passage through the intestinal wall and p-hydroxyphenylacetic acid ( p-OHPA) was the only metabolite found in venous plasma from the loop (mean ratio p-OHPA/TYR = 5). Oral or intravenous pretreatment with the monoamine oxidase (MAO) inhibitors tranylcypromine or MD780515 significantly lowered the ratio of p-OHPA/TYR (range = 0.2–1.1) measured 3hr after the last dose. Twenty-four hours after the last dose of MAO inhibitor p-OHPA/TYR ratios in dogs pretreated orally with MD780515 had returned to control levels while ratios in dogs pretreated orally with tranylcypromine remained low (mean = 1.6). In vitro rates of deamination of the substrates 5-hydroxytryptamine (selective for the A form of MAO) and β-phenylethylamine (selective for the B form of MAO) in homogenates of intestine paralleled the in vivo findings in most cases. Tranylcypromine produced a nonselective irreversible inhibition of both MAO-A and MAO-B whereas MD780515 was found to be a selective inhibitor of MAO-A and also appeared to be reversible.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.