Two erythroleukemia cell lines have been established from the splenic lesio
ns of red blood cell-type pyruvate kinase (R-PK) activity-deficient mice of
CBA/N origin infected with a polycythemic strain of Friend leukemia virus
complex (FVp). Ten to 30 % of the cells of these cell lines undergo apoptot
ic changes in routine passage, as shown by nuclear fragmentation, DNA ladde
ring, DNA content (propidium iodide (PI) staining), and annexin V binding a
ssay. In these cells, however, although adenosine 5'-triphosphate (ATP) lev
els were lower than in the control cells, the mitochondrial inner transmemb
rane potential (Delta psi(m)), detected by rhodamine 123 (R123) and diSC(3)
(5) staining, remained unchanged until the final stage of apoptosis, No evi
dence was obtained to relate this finding to R-PK mutation due to difficult
y in cloning stable, conditionally inducible R-PK gene transfectants. Howev
er, low Delta psi(m), in the apoptotic cell population of the control T3-K-
1 (K-l) and T3-Cl-2-0 (2-0) Friend erythroleukemia cells supports a possibl
e relationship, as do results obtained in two Friend erythroleukemia cells
recently isolated from normal CBA/N mice. These cell lines are expected to
be useful for clarifying both the primary apoptotic changes independent of
mitochondrial dysfunction and the PK-isozyme changes during erythrodifferen
tiation, for example, the decreased muscle type 2 (M2) PK level. Modificati
on of growth signals in these cell lines may modulate differentiation and/o
r apoptosis and allow further elucidation of the signaling networks.