Mitochondrial DNA analysis of mouse-rat hybrid cells: effect of chloramphenicol selection on the relative amounts of parental mitochondrial DNAs.

Several mouse-rat somatic hybrid cell lines were isolated by fusing chloramphenicol-resistant (CAPr) and CAP-sensitive (CAPs) parent cells, and propagation of the parent mitochondrial DNA (mtDNA) species in the hybrid cells was studied. The restriction endonucleases EcoRI, HpaII, and HaeIII were used for identification of mtDNA species. Both mouse and rat mtDNAs were propagated in all the hybrid cells examined and maintained during long-term cultivation and repeated cell division. Moreover, in CAPr mouse-rat hybrid cells, selection and successive cultivation in the presence of CAP did not increase the relative amount of mtDNA species of CAPr parent cell origin, and when CAP was removed from the culture medium, mtDNA species of CAPr parent cell origin did not decrease appreciably. The amount of mouse mtDNAs was consistently 1-4 times that of rat mtDNAs inthe mouse-rat hybrid cells regardless of the species of parent cells from which the CAP resistance was derived. Thus mouse-rat hybrid cells have a stable mtDNA population in which the amount of mouse mtDNAs is larger than that of rat mtDNAs without any influence of CAP selection.