MULTIPLE SPECIFIC CHROMOSOMAL ALTERATIONS IN A RAT ASCITIC HISTIOCYTOMA AK-5

In the rat ascitic histiocytoma, AK-5, chromosome numbers vary between 33 and 41 with a peak at 40 chromosomes. None of the metaphase spread s showed double minute chromosomes. The karyotype of this tumor was ch aracterized;ecl by hypodiploid chromosome constitution. Giemsa banding analysis revealed 12 clonal marker chromosomes (M1-M12). Tentative id entification of these markers M1 = ins(1a); M2 = t(5;?); M3 = t(8;10); M4 = t(8;?); M5 = t(10;X); M6 - t(l5;?); M7 = t(5;6); M8 = del(13p); M9-M12 = unidentified. M3 being a large near metacentric chromosome se rves as a characteristic marker for this tumor: All marker chromosomes except M2 and M4 were present in single copy per cell. In some metaph ases M2 was present in 2 copies while M4 was present in 2 ol 3 copies per cell. The total cell cycle duration of AK-5 cells was 15.5 h and t he different phases, G1, S, G2+M were estimated as 1.2, 12.2, and 2 h, respectively.