[Determination of metabolizing activities of xenobiotic tissue in rat embryo fibroblasts].

Rat embryo fibroblast suspensions were prepared from 19-day-old wistar rat fetuses by trypsin digestion of the minced fetal tissue. Drug-metabolizing capability of isolated viable rat embryo cells on 7-ethoxycoumarin and 1,3-cyclohexadiene has been investigated. The biotransformation of 7-ethoxycoumarin represents a suitable experimental tool to measure the level and significance of the Phase I and Phase II metabolism systems. We estimated the mixed-function oxidation by the fluorimetric measurement of "unconjugated" 7-hydroxycoumarin in the incubation medium while the conjugates formation was determined by subsequent hydrolysis with beta-glucuronidase and aryl sulphatase. 1,3-Cyclohexadiene was selected as a substrate for mixed-function oxidation for a useful comparison of drug-metabolizing capability in isolated viable rat embryo cells with rat hepatocytes. When 1,3-cyclohexadiene was incubated with rat embryo fibroblasts for different times, cyclohexene-1,2-diol resulted to be the main metabolite. Cyclohexene-1,4-diol was detected only in traces. Therefore the metabolic pathway of 1,3-cyclohexadiene with rat embryo cells, as well as isolated hepatocytes, involves the intermediate formation of the 3,4-epoxycyclohexene, that is rapidly hydrolyzed to diols by a non enzymatic process.