Cytogenetic studies on rat leukemia induced by pulse doses of 7,12-dimethylbenz(alpha)anthracene.

Abstract

Summary Cytogenetic studies were carried out on bone marrow and spleen cells of 40 rats of Long-Evans strain with primary leukemia induced by pulse doses of 7,12-dimethylbenz(α)anthracene. Chromosomal abnormalities were detected in 26 cases, of which 21 were characterized by abnormal constitution of two specific chromosomes, C-1 (longest telocentric chromosome), and A-6 (6th group of metacentrics). Most of the leukemias represented the hepatic type. Sixteen rats had modal or nonmodal cells with trisomic C-1 chromosome, 5 among them containing stem-line cells with both C-1 and A-6 trisomy. Unassociated A-6 trisomy was found in modal cells of 4 other leukemias, one of them chloroleukemia, and in the stemline of one of the trisomic C-1 positive leukemia. Modal hypodiploid cells of 41 chromosomes with A-6 monosomy was also detected in one case. These consistent chromosomal abnormalities appear to be the first so far reported for an experimental leukemia. The presence of a marker chromosome, metacentric or submetacentric, was recognized in cells of 4 other leukemias. The remaining one had tetraploid cells. No chromosomal anomaly could be detected in 12 other hepatic type leukemias, one lymphoblastic and another thymic. The possible interpretation for the presence of consistent chromosomal abnormalities in the given type of leukemia is discussed.