Skin disc analysis. In a skin metabolismstudy, rat skin was prepared
and mounted in the cells as described above. The skin was treated with
bifenthrin, deltamethrin or cis-permethrin (5 μCi, 100 nmol,
312.5 nmol/cm2) in acetone. Following a 24 h exposure, the skin was
washed as described above and then stored at−70 °C in a scintillation
vial until analyzed. For analysis, the skin was thawed, tape-stripped ten
times, and homogenized in 4 ml of receptor fluid (without fetal bovine
serum) using a polytron homogenizer. Tenmilliliters of methanol were
added to the homogenate and then itwas vortexed vigorously, followed
by centrifugation. The supernatant was removed. Ten milliliters of
methanol were added to the pellet, followed by vortexing and
centrifugation. The supernatants were combined, taken to dryness
under a stream of nitrogen, reconstituted in 0.5 ml HPLC mobile phase
(water/methanol, 10/90) and centrifuged through a 0.2 μmfilter. These
samples were analyzed by HPLC as described above.