UNUSUALLY HIGH INCIDENCE OF SPONTANEOUS CHROMOSOMAL ABERRATIONS IN MOUSE PRIMARY CELL CULTURE

Abstract

Fibroblast cultures established from mouse embryos showed an abnormally high incidence of spontaneous chromosomal aberrations at early passages. The aberration frequency reached a peak (39.5%) at the 4th passage (13 days after initiation of the cultures), and then declined gradually. Culture media collected from the mouse cultures were found to be capable of inducing chromosomal aberrations in Chinese hamster cells. This indicates that some chromosome-damaging substances had evolved in the mouse primary cultures and were secreted into the culture medium. These substances seemed to affect cells very rapidly, since the production of chromosomal aberrations was detected as early as 2h after Chinese hamster cells were exposed to the conditioned medium derived from the mouse cultures. The substances appeared to be heat-labile, as the mouse conditioned medium lost its chromosome-damaging effect when it was prewarmed at 37°C for 24h. The nature of these toxic substances is, however, yet unknown. Preliminary studies on the primary cultures derived from other mammals imply that the phenomenon reported here is specific to certain groups of mammals except primates.