Role of monoamine oxidase A and B in the deamination of newly-formed dopamine in the rat kidney.

The present study has examined the effects of two selective inhibitors of monoamine oxidase (MAO) type A and B, respectively Ro 41-1049 and Ro 19-6327, on the deamination of newly-synthesized dopamine in kidney slices incubated with exogenous L-DOPA (50 and 100 mumol/l). Ro 41-1049 (50, 100 and 250 nmol/l) was found to produce a concentration-dependent increase of newly-formed dopamine (36-56% increase) and reduced DOPAC formation (45-86% reduction). Ro 19-6327 (50, 100 and 250 nmol/l), was found not to affect the accumulation of newly-formed dopamine at 50 mumol/l L-DOPA in the medium, but significantly reduced the formation of DOPAC. At the concentration of 100 mumol/l of L-DOPA, Ro 19-6327 (100 and 250 nmol/l) significantly increased (by 32% and 132%, respectively), the dopamine tissue levels in kidney slices and decreased DOPAC formation. It is concluded that both MAO-A and MAO-B are important in the metabolism of newly-formed dopamine in kidney slices incubated with exogenous L-DOPA.