Abstract
Friend leukemia cells (FLC) are nucleated erythroid precursors, and are markedly stimulated towards more advanced stages of differentiation by treatment with dimethyl sulfoxide (DMSO). The presence of spectrin, an erythrocyte membrane protein, has been investigated in untreated and in DMSO‐treated FLC by indirect immunofluorescence and by analysis in SDS‐polyacrylamide gel electrophoresis of low‐ionic‐strength cell extracts immuno‐precipitated with a monospecific anti‐spectrin serum.
Spectrin is detectable in significant amounts in the “inducible” clones prior to DMSO stimulation, and accumulates 4‐ to 5‐fold upon addition of this compound to the cultures. Spectrin accumulation occurs rather early (24 hours after cell seeding) and reaches its peak on the third day, to decline thereafter. Semiquantitative determinations of spectrin amounts present in DMSO‐stimulated 745A and A°1 cells on the third day after treatment were 2.4 × 10^5^ and 3.0 × 10^5^ molecules/cell, respectively.
Spectrin is also detectable in very low amounts in an “uninducible” line of FLC, and is not accumulated upon DMSO treatment thereof, whereas treatment with hemin does cause a significant increase of spectrin‐positive cells.
These data indicate that spectrin is a convenient “early” marker for in vitro studies of erythropoiesis.