Effects of Dichlorvos and Characterization of Microsomal Nadph-cytochrome P450 and Nadh-ferricyanide Reductase in Rainbow Trout (oncorhynchus Mykiss) Liver

The kinetics of oxidation of rainbow trout (Oncorhynchus mykiss) NADPH-cytochrome P450 reductase (NCPR) by cytochrome-c and NADH-ferricyanide reductase (NFR) by K3Fe(CN)6 were studied. NCPR and NFR activities from liver microsomes of rainbow trout (Oncorhynchus mykiss) had a specific activity of 0.0246 and 0.0350 nmoles/min/mg protein, respectively. The maximal rate of NCPR reaction was found at cytochrome-c concentrations above 2.1 mM and in the presence of cyt c. Vmax and Km were 0.0083 nmoles/min/mg and 1.14 mM. The maximal rate of NFR reaction was at K3Fe(CN)6 concentrations higher than 2.0 mM and in the presence of K3Fe(CN)6. Vmax and Km values were 1.04 nmoles/min/mg and 0.352 mM, respectively. The inhibition by dichlorvos (DDVP) on NCPR and NFR activity was not exhibited over the range 1.0-5.0 mM DDVP. Introduction DDVP is an organophosphate medicine, used to treat farmed salmon infested with ectoparastic crustacean sea lice (Murison et al., 1997; McHenery et al., 1997). A clinical pharmacological study was carried out to evaluate the pharmacokinetics of metrifonate and its active metabolite DDVP (Heinig et al., 1999). Chronic DDVP treatment and early electrophysiological changes were investigated in three series of experiments (Desi et al., 1999). DDVP is usually used as a veterinary medicine to protect farmed salmon against * Corresponding author. Tel.: +90-362-4576020, ext. 5199, fax: +90-362-4578081, e-mail: [email protected]