(The) antimutagenic effect of sodium selenite against benzo(a)phrene in CHO cells and salmonella typhimurium

Abstract

Benzo(a)pyrene was observed to be mutagenic only in the presence of S9 fraction in S. typhimurium TA98. The number of His$^+$ revertants increased in proportion to the level of B(a)P. The lethality showed up over $10 \mu g/plate$. Sodium selenite was not mutagenic in the range of 0-10 g/plate, nor activated by S9 fraction. It supports selenium``s promptness in suppressing the mutation by a large part. On the contrary to B(a)P``s cytotoxic effect and inhibition of cell growth as well as its mutagenicity, selenite was observed to promote the cell growth with very little mutagenic effect. Moreover, selenite of growth promoting concentrations($\sim{6\times{10^{-8}}$M) significantly reduced the incidences of mutation (to about 50\%) induced with B(a)P 0.5 g/ml. This result suggests selenium``s ability of suppressing mutation is not attributable to only its growth inhibition of tumor cells. This study clarified that selenium of nonmutagenic level($\sim 6\times{10^{-8}}$M)could able to prevent carcinogenesis at the early initiation phase.