Fate of fluazifop butyl in rat and human skin in vitro.

Enzyme mediated hydrolysis of fluazifop butyl has been measured with rat and human skin post-mitochondrial fractions. Rat skin had a ten times greater capacity to metabolise fluazifop butyl than human skin, but the enzyme affinities were similar. The post-mitochondrial fraction metabolism was compared to that seen during absorption in a flow through diffusion cell with viable skin. Limited hydrolysis of absorbed fluazifop butyl was seen in rat skin, but increased two fold if the stratum corneum was removed. The stratum corneum was found to retain fluazifop butyl. When the skin was pre-incubated with the esterase inhibitor bis (p-nitrophenol) phosphate (BNPP), reduced metabolism was seen. No metabolism of fluazifop butyl was seen in human skin during absorption. Retention of the compound by the stratum corneum is postulated to restrict the accessibility of the compound to the enzyme site, thus influencing the observed metabolism during the absorption process.