次黄嘌呤对单胺氧化酶的抑制作用

实验证明给小鼠po次黄嘌呤25～500 mg/kg时,对肝和脑中单胺氧化酶B(MAOB)活性的抑制作用与剂量成明显的量—效关系,对MAO-A活性的抑制较弱,且无明显的量—效关系。给小鼠一次po次黄嘌呤500 mg/kg,于给药后16h,对MAO抑制作用最明显。sc时,对肝中MAO活性抑制也以给药后16 h最明显,但对脑中MAO活性抑制不明显。离体实验证明,次黄嘌呤对MAO-B的抑制为竞争性,对MAO-A则为混合型抑制。

INHIBITORY EFFECT OF HYPOXANTHINE ON MONOAMINE OXIDASE ACTIVITY

Hypoxanthine was demonstrated to have a dose-dependent inhibitory effect on type B monoamine oxidase (MAO-B) activity in liver and brain tissues, and slight inhibitory effect on type A MAO(MAO-A) activity when given orally to mice at doses of 25-500 mg/kg. When mice were given orally hypoxanthine 500 mg/kg, MAO-A and -B activities were all inhibited significantly 16 hours after administration, but the inhibitory action on MAO-A was weaker. Subcutaneous injection of the agent also produced obvious inhibition of MAO activity in the liver but no significant influence on MAO activity in brain tissue was observed. In vitro experiment showed that the action of hypoxanthine on MAO-B was competitive inhibition and that on MAO-A was competitive mixed with noncompetitive inhibition.