CHARACTERIZATION AND APPLICABILITY OF A CYTOTOXICITY ASSAY DETERMINING GROWTH-INHIBITION AFTER A 1-HOUR TREATMENT WITH XENOBIOTICS IN HUMANCELL-CULTURE

A cytotoxicity assay to determine growth inhibition after a 1-hr treat ment with xenobiotics in serum-free medium and subsequent re-incubatio n in serum-containing medium without test chemicals was characterized and optimized for cytotoxicity screening. Our results indicated that a fter treatment of human fibroblasts with the test chemicals a 44-hr re -incubation period is most suitable for measuring the growth inhibitor y effects of a broad spectrum of chemicals. Applying the assay, the ac tivity to inhibit growth by 10% (log IC10) correlated with the lipophi licity (specified as octanol-water partition coefficient = log K-ow) o f 19 xenobiotics. The linear regression coefficient was r = 0.91. This close correlation between toxicity and lipophilicity shows that the t est, which avoids long-term incubation in serum-containing medium, is suitable for cytotoxicity screening and structure-activity analysis.