Pargyline, a monoamine oxidase inhibitor, is an antihypertensive agent. We report on the ability of pargyline to inhibit the oxidative deamination of norepinephrine (NE) and 2-phenylethylamine (PEA) by rat heart and mesenteric artery. The cardiovascular tissues appear to contain amine oxidases that are quite different from those of brain. For example, pargyline, when tested in vitro or administered to rats, did not differentially block the deamination of NE and PEA as it does in brain. Moreover. there is a PEA oxidase activity that is blocked by pargyline and an activity that is resistant to pargyline but blocked by semicarbazide or cuprizone. PEA oxidase activity can be differentiated from NE oxidase activity by thermal stability. The pargyline-resistant PEA oxidase activity may be related to a connective tissue amine oxidase.
