UPTAKE, TISSUE DISTRIBUTION, AND METABOLISM OF MALACHITE GREEN IN THECHANNEL CATFISH (ICTALURUS-PUNCTATUS)

The disposition of malachite green was determined in channel catfish ( Ictalurus punctatus) after intravascular dosing (0.8 mg . kg(-1)) or w aterborne exposure (0.8 mg . L(-1) for 1 h). After intravascular dosin g, mean plasma concentrations of the parent compound exhibited a triph asic decline with a terminal elimination half-life of 6.2 h. Malachite green was rapidly absorbed and concentrated in the tissues during wat erborne exposure. The rate of accumulation was directly related to pH of the exposure water. After waterborne exposure, elimination of the p arent compound from plasma also was triphasic with a terminal half-lif e of 4.7 h. In muscle, the half-life of the parent compound was approx imately 67 h. Malachite green and its metabolites were widely distribu ted in all tissues. In fish exposed to C-14-labeled malachite green, t otal drug equivalent concentrations were highest in abdominal fat and lowest in plasma. Malachite green was rapidly and extensively metaboli zed to its reduced form, leucomalachite green, which was slowly elimin ated from the tissues. Leucomalachite green is an appropriate target a nalyte for monitoring exposure of channel catfish to this drug.