MUTAGENICITY EVALUATION STUDIES IN THE RAT BONE MARROW CYTOGENETIC ASSAY IN THE MOUSE LYMPHOMA FORWARD MUTATION ASSAY CATALYTIC CRACKED CLARIFIED OIL API Sample 81-15
Abstract Chromosome aberrations were determined in the bone marrow cells of Sprague-Dawley rats subchronically exposed per os to API #81-15 (five daily doses). Three dose levels were employed: 1 g/kg/day@ 0.3 g/kg/day and 0.1 g/kg/day. Bone marrow was sampled six hours after the last dose. Ten male and ten female animals were exposed to the low@ medium and negative control dose levels. Thirteen animals of each sex were exposed at the high dose level to account for toxicity; however@ only ten animals were cytogenetically analyzed for either sex. The structural aberration frequency in bone marrow cells of rats exposed to API #81-15 did not differ significantly from the negative control at any tested dose. The percentages of cells showing one or more structural aberrations or two or more structural aberrations were likewise similar to the negative controls@ as was the frequency of numerical aberrations. These results were the same whether males or females or both sexes pooled were evaluated by the Student t-test. A concurrent positive control substance@ triethylenemelamine@ showed significant increases in structural aberration frequency at two dose levels. For in vitro treatments of the mouse lymphoma cell line@ L5178Y@ the mutant frequency at the thymidine kinase (TK) locus was significantly increased. The cells were exposed to #81-15 for four hours in the presence and absence of rat liver S9 metabolic activation. API #81-15 was insoluble at 61.5 nl/ml without activation and at 31.3 nl/ml in the presence of metabolic activation. Under nonactivation conditions@ #81-15 was assayed at an applied concentration range of 7.81 nl/ml to 125 nl/ml and a small but significant increase in the mutant frequency was induced at 125 nl/ml where #81-15 was moderately toxic. In the presence of the activation mix@ API #81-15 was converted to a more toxic form or forms. Significant@ dose-dependent increases in the mutant frequency were induced from 1.95 nl/ml to 31.3 nl/ml where moderate to very high toxicities were induced. API #81-15 was therefore evaluated as active in the mouse lymphoma cell system.