AJP - Cell Physiology, Vol 264, Issue 2 C311-C316, Copyright © 1993 by American Physiological Society
Na(+)-K(+)-ATPase subunit isoform pattern modification by mitogenic insulin concentration in 3T3-L1 preadipocytes
J. J. Russo and K. J. Sweadner
Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
When 3T3 preadipocyte cell lines are induced to differentiate to the
adipocyte phenotype, the expression of Na(+)-K(+)-ATPase isoforms changes.
Some disparities have been noted by investigators who used different
hormonal conditions to stimulate adipocyte conversion, however. In the
present report we investigated the effect of high concentrations of insulin
on the 3T3-L1 cell line, to determine whether it affected Na(+)-K(+)-ATPase
expression separately from its ability to promote phenotypic conversion.
The effect of insulin was compared with that of dexamethasone and
3-isobutyl-1-methylxanthine. Changes in Na(+)-K(+)-ATPase subunit
expression were seen regardless of the hormonal stimulus. Induction of
alpha 2-mRNA and reduction of beta 1-mRNA were always observed. At the
protein level, too, induction of alpha 2-protein was noted; alpha 1-protein
levels were not markedly affected. The change in alpha-isoform protein and
mRNA levels did not correspond quantitatively with the fraction of cells
that were morphologically converted, suggesting that it is an early event
in differentiation.
