Characterization of ouabain-resistant mutants of the preadipocyte Ob17 clonal line. Adipose conversion in vitro and in vivo.

After exposure to a mutagenic drug (ethylmethanesulfonate), mutant clones of Ob17 preadipose cells resistant to the cytotoxic action of ouabain have been isolated. Their ability to grow in serum-supplemented medium containing greater than or equal to 3 mM ouabain is consistent with the decreased ouabain sensitivity of K+ transport observed in one of these clones (Ob17-OR11). Ouabain-resistant mutants retain their ability to convert into adipose-like cells in vitro with a frequency similar to that of original Ob17 cells. Long-term maintenance of Ob17-OR11 cells in ouabain-enriched medium leads to a higher frequency of adipose conversion, which is linked to a rather specific and limited growth-promoting effect of the drug. Undifferentiated Ob17-OR11 cells, when injected subcutaneously into athymic mouse, give rise in vivo to a fat pad containing ouabain-resistant mature adipocytes. Therefore, Ob17-OR11 clone should be a useful tool to distinguish in vivo between intrinsic and extrinsic factors involved in the differentiation of adipose precursor cells.