CLASTOGENICITY OF METHAPYRILENE HYDROCHLORIDE IN CULTURED CHINESE-HAMSTER CELLS

The antihistaminic agent methapyrilene hydrochloride (MPH, CAS No. 135 -23-9) has been reported as a potent rat hepatocarcinogen. However, ne ither the action mechanism nor mutagenicity of MPH have been clearly e lucidated yet. Chromosomal aberration (CA) tests were performed with M PH in CHO-K1-BH4 and CHL cells without a metabolic activation system. Isochromatid break-like aberrations were observed in metaphases of CHO -K1-BH4 cells treated with MPH. MPH induced CA more effectively at hig her pH in equitoxicity base. In contrast to CHO-K1-BH4 cells, typical chromatid type exchanges were observed in CHL cells treated with MPH. These results clearly support the results of other researchers that MP H induce chromosomal aberration and imply that MPH induces cancer in a nimal via other mechanisms than mere DNA damage or gene mutation which had been nearly proven to be negative by many. researchers. It was su ggested that pH variation might increase the sensitivity of CA tests f or certain category of chemicals with dissociation potential.