[Inhibition of delta-aminolevulinic acid dehydratase by styrene and styrene oxide]

Effects of styrene and styrene oxide on delta-aminolevulinic acid dehydratase in rats were investigated, in vivo and in vitro. In the in vivo study, rats were exposed to styrene or styrene oxide intraperitoneally for seven days. delta-Aminolevulinic acid dehydratase in the erythrocyte was inhibited by both styrene and styrene oxide. The inhibition by styrene oxide had a clear dose-response relationship, but that by styrene did not. In the liver, however, these substances did not inhibit delta-aminolevulinic acid dehydratase. In the in vitro study, styrene oxide inhibited delta-aminolevulinic acid dehydratase both in the erythrocyte and in the liver, but styrene failed to inhibit it. These results suggest that styrene is metabolized to styrene oxide, and this metabolite inhibits delta-aminolevulinic acid dehydratase. It is also thought that the discrepancy of inhibition between the erythrocyte and the liver is due to a difference of distribution and metabolism of the substances.