You are here:
IN VITRO METABOLISM OF PYRETHROIDS IN RAT LIVER MICROSOMES
Citation:
Godin, S. J., R A. Harrison, M F. Hughes, AND M J. DeVito. IN VITRO METABOLISM OF PYRETHROIDS IN RAT LIVER MICROSOMES. Presented at Society of Toxicology, Baltimore, MD, March 21-25, 2004.
Description:
IN VITRO METABOLISM OF PYRETHROIDS IN RAT LIVER MICROSOMES
SJ Godin1, RA Harrison2 MF. Hughes 2, MJ DeVito2; 1Curriculum In Toxicology, UNC-CH, Chapel Hill NC, USA; 2ETD, NHEERL, ORD, US EPA, RTP, NC, 27711, USA.
Pyrethroids are neurotoxic pesticides that bind to sodium channels. These pesticides are used in a variety of agricultural and household applications. In order to determine in vitro kinetic parameters for pyrethroids, an LC/MS method was developed for the detection and quantification for deltamethrin, esfenvalerate and cyfluthrin. These chemicals were separated using a Zorbax Eclipse XDB -C18 column (4.6 x 50 mm, 3.5 micron) and an isocratic mobile phase of 90:10 methanol:water with 0.01% formic acid. Using a flow rate of 0.5 ml/minute all chemicals were separated and eluted within 5 minutes. In our LC/MS system (Agilent 1100 series ion trap LC/MS) all three chemicals formed sodium adducts. The adducted molecular ions used to quantify these chemicals were m/z 527.8, 442.1 and 456.0 for deltamethrin, esfenvalerate and cyfluthrin, respectively. Detection limits were as low as10 ng/ml. Initial kinetic studies were performed with deltamethrin. Liver microsomes were prepared from 65 day old male Long Evans rats. The in vitro assay was performed in 1ml of 100 mM Tris (pH 7.5), 1 mg/ml NADPH and 1mg microsomal protein/ml. The reaction was carried out for 0, 5, 10, 20, and 30min, and was done in duplicate. The reaction was started with the addition of deltamethrin at concentrations ranging from 2 - 200nM. The reaction was stopped by the addition of 5 ml of cold n-pentane. Extraction efficiencies were greater than 80%. Nonlinear regression analysis was used to estimate Km and Vmax. Estimates of Km and Vmax for are 53.8 nM and 185 pmoles/min/mg protein, respectively. (This abstract does not represent USEPA policy. SJG supported by NHEERL-DESE, EPA CT826513)