Regular article :AATEX3(1):1-8
Butylated hydroxytoluene (BHT, 3, 5-ditert-butyl-4-hydroxytoluene) and 4-hydroxy-4-methyl-2,6-di-t-butylcyclohexa-2,5-dienone (BHTOH) were assayed using cell culture methods for assessing potential teratogenicity. In the rat embryonic cell differentiation assay, BHT and BHTOH showed similar inhibitory effects on the differentiation of both midbrain (MB) and limb bud (LB) cells. From the dose-response curve, the concentrations of BHT and BHTOH that inhibited the production of differentiated foci by 50%) IC50) in MB ceils were 254 and 245 ƒÊM, respectively. The inhibitory action of BHT on the human embryonic palatal mesenchymal (HEPM) cell growth was increased in the presence of S-9 mix prepared using livers from untreated f344 rats and from those treated with phenobarbital and 5,6-benzoflavone (PB-BF). In the HEPM cell growth assay, hamster and mouse PB-BF-induced S-9 were also effective in causing the metabolic activation of BHT. In vivo/in vitro methods for determining teratogenicity were investigated using a rat embryonic cell differentiation assay. BHT was orally administered to pregnant rats at a dose of 1000 mg/kg on day 11 of gestation. Embryonic MB and LB cells were then prepared from day-12 embryos, and cultured. The differentiated foci slightly reduced to 92-94% of the control values in MB and LB cultures. It was assumed that BHT up to 1000 mg/kg as a single oral dose was not harmful to the rat embryos during organogenesis under our experimental conditions.