IC50: 11.52 nM: inhibits monoamine oxidase (MAO) type A (MAO-A).

IC50: 8.2 nM: blocks MAO type B (MAO-B).

Pargyline, an irreversible and non-selective inhibitor of MAO, is used to treat moderate hypertension and cancer cells. There are two isoforms of MAO, MAO-A and MAO-B. MAO-A preferentially deaminates melatonin, serotonin, norepinephrine and epinephrine. MAO-B catalyzes the oxidative deamination and inactivation of certain catecholamines within the presynaptic nerve terminals.

In vitro: Pargyline reduced the proliferation of human prostate carcinoma (LNCaP-LN3) cells in a time- and dose-dependent fashion. In addition, compared to the control, pargyline remarkably triggered cell cycle arrest at the G1 phase. Pargyline elicited an increase in the cell death rate via promoting apoptosis, suggesting that pargyline was a powerful candidate drug for the treatment of human prostate cancer [1].

In vivo: Male rats were injected intraperitoneally pargyline at a dose of 75 mg/kg for 80 min. Pargyline significantly increased the concentration of extracellular dopamine in the striatum and simultaneously, significantly reduced the concentration of extracellular MAO-derived metabolite 3,4-dihydroxyphenylacetic acid to undetectable levels [2].

References:
[1].  Chai, Y. Effects of the monoamine oxidase inhibitors pargyline and tranylcypromine on cellular proliferation in human prostate cancer cells. Oncology Reports. 2013.
[2].  Desvignes, C., Bert, L., Vinet, L., Denoroy, L., Renaud, B., & Lambás-Seas, L. Evidence that the neuronal nitric oxide synthase inhibitor 7-nitroindazole inhibits monoamine oxidase in the rat: in vivo effects on extracellular striatal dopamine and 3,4-dihydroxyphenylacetic acid. Neuroscience Letters. 1999; 261(3):175-178.