An in vitro method for toxicity evaluation of water-soluble substances.

The purpose of the present investigation was to develop a simple method for the evaluation of reversible and irreversible toxic influences in a cell culture system. A cell monolayer established on the bottom of glass scintillation vials was exposed to a toxic substance (phenol). Changes in the DNA synthesis of the cells were utilized as a criterion of toxic influence, and were measured by recording the incorporation of tritium labelled thymidine using a liquid scintillation technique. The exposure of the cells to phenol caused a marked decrease in the rate of DNA synthesis when the phenol concentration was increased from 0.01 to 0.1%. The decrease in the DNA synthesis could be reversed by maintaining the cells in growth medium for 4 hours after the cell-phenol contact. The degree of reversibility was dependent on the cell-phenol contact time, the phenol concentration, and the cell line used. The simple test procedures and the quick and convenient obtainment of results simplify the assay of large test series and make the method particularly useful for screening tests.