title: Time and concentration dependent accumulation of [3H]-deltamethrin in Xenopus laevis oocytes.
abstract: A primary target of pyrethroid insecticides are the voltage-sensitive sodium channels (VSSCs). Expression of VSSCs in oocytes from Xenopus laevis is an experimental model used to study the effects of pyrethroids. A common assumption when utilizing this model is that media concentration is an accurate substitute for tissue dose. This assumption may not hold true for lipophilic chemicals. [3H]-deltamethrin (DLT) was used to test the hypothesis that media concentration is a good surrogate for tissue concentration. Accumulation of DLT (0.001-10 microM) in non-transfected oocytes exposed for 20 min was determined using liquid scintillation counting. The time course (1.0-180 min) of tissue accumulation of DLT (approximately 1.0 microM (0.50 ppm) in media) was also determined. Results demonstrate that tissue dose increases as a function of time with media concentration underestimating tissue dose at long incubation times (approximately 2.0-fold at 180 min) and overestimating tissue dose short incubation times (approximately 8.6-fold at 5 min). Tissue dose increases as a function of media concentration, with overestimation of tissue dose ranging from 1.5-fold at 0.0005 ppm to 4.1-fold at 5.0 ppm. These data suggest that media concentration does not accurately predict tissue dose at all times for a broad range of deltamethrin concentrations in X. laevis oocytes.
authors.affiliation: Curriculum in Toxicology, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Harrill
authors.forename: Connie A
authors.initials: CA
authors.lastname: Meacham
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Shafer
authors.forename: Michael F
authors.initials: MF
authors.lastname: Hughes
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Crofton
mesh_terms: D000818:Animals; D003470:Culture Media; D004305:Dose-Response Relationship, Drug; D005260:Female; D005544:Forecasting; D007306:Insecticides / Q000493:pharmacokinetics*; D009570:Nitriles; D009865:Oocytes; D011722:Pyrethrins / Q000493:pharmacokinetics*; D015203:Reproducibility of Results; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D003470:Culture Media; D007306:Insecticides; D009570:Nitriles; D011722:Pyrethrins; C017180:decamethrin