A diploid rat liver cell culture. III. Characterization of the heteroploid morphological variants which develop with time in culture.

A substrain was developed from one of three morphological variants which were isolated from a late passage cloned epithelial rat liver cell strain. The substrain was studied at sequential passages, over time, with respect to clonal morphology, growth, plating efficiency, packed cell volume, saturation density, chromosome number, karyology, ability to grow in soft agar, and degree of malignant transformation. The substrain was determined to be the progenitor of the other two morphological variants and the progression in morphological variance follows the stemline hypothesis. A marker chromosome was found to be a stable component of the genetic constitution of all cells in the substrain. What is observed appears to be population growth dynamics concomitant with a cellular aging phenomenon.