Inhibition of monoamine oxidase-A of rat brain by pyrethroids--an in vitro kinetic study.

An in vitro kinetic study on inhibition of the monoamine oxidase-A (MAO-A) of the rat brain by two pyrethroids, namely permethrin (PM) and cypermethrin (CPM), has shown that PM and CPM competitively inhibit MAO-A by altering both the Michaelis-Menten constant (Km) and the maximum velocity (Vmax). Inhibitor constant values (Ki) indicated that CPM was a more effective inhibitor of MAO-A than PM. Both PM and CPM caused maximum inhibition of MAO-A at neutral pH. CPM significantly elevated the activation energy values of MAO-A as compared to those of PM.