Effects of an acridine half‐mustard (ICR 191) on growth and ploidy of frog cells in culture

The effects of an acridine half‐mustard, ICR 191, on the growth rate and ploidy of four haploid and two diploid lines of Rana pipiens cells in culture were studied. Growth curves indicate that the haploid and diploid cell lines were equally resistant to a 4‐hour exposure of this drug (0.1 μM to 10 μM). ICR 191 treatment induced the haploid cell cultures to become diploid. The proportion of diploid cells increased progressively with respect to time after the 4‐hour exposure period. The greater the concentration of ICR 191 applied, the more rapid the rate of conversion. Autoradiographic determinations of percent labelled nuclei indicate that DNA synthesis was not inhibited in haploid or in diploid cells. Therefore, the increased proportion of diploid cells did not originate from the small percentage of diploid cells in the initial population. Instead, the haploid cells were converted to diploid cells. Time lapse cinematography indicated that the conversion mechanism was other than cell fusion. Conversion to higher ploidy did not occur when diploid cell cultures were exposed to ICR 191.