The Effect of Monoamine Oxidase and Diamine Oxidase Inhibitors on Norepinephrine and Histamine in Rat Heart

摘要

The effect of several hydrazine and nonhydrazine compounds on the concentrations of norepinephrine and histamine in the rat heart was studied. The compounds used were either monoamine oxidase (MAO) or diamine oxidase (DAO) inhibitors. Hydrazine (0.31 mmole/kg.), monomethylhydrazine (0.31 mmole/kg.), pargyline (0.16 mmole/kg.), and tranylcypromine (0.16 mmole/kg.) produced significant elevations of norepinephrine in the heart. The increase produced by monomethylhydrazine (MMH), pargyline, and tranylcypromine may be due to the fact that they are potent MAO inhibitors, but this does not explain the effect of hydrazine which is devoid of any MAO inhibitory action. Histamine levels in the heart were elevated only by MMH (0.31 mmole/kg.) and pargyline (0.16 mmole/kg.). MMH inhibited DAO, but pargyline does not have any effect on this enzyme. The mechanism whereby hydrazine increased norepinephrine in heart and pargyline elevated histamine does not appear to be dependent on their ability to inhibit the enzymes connected with the metabolism of these two amines. These experiments indicate that the extent of MAO or DAO inhibition by a specific compound is not related to its ability to affect tissue amine levels. The data also show that exposure to MMH or hydrazine could affect the cardiovascular system by changing the levels of amines in the heart. (Author)