Modulation by dexamethasone of insulin binding and insulin receptor mRNA levels in U-937 human promonocytic cells.
Treatment with 5 x 10(-6) M dexamethasone stimulated insulin binding in human promonocytic U-937 cells. When curvilinear Scatchard plots were examined according to the one-site model, only changes in affinity, but not in receptor numbers, were observed. However, when the two-site model was applied, an increase in both the affinity and the number of the high affinity-low capacity sites was observed, with maximum values at 15 h. By contrast, the low affinity-high capacity sites did not undergo significant alterations. Northern blot assays revealed two insulin receptor-related mRNAs of approximately 11 and 7 kb in size. Dexamethasone increased the levels of these RNAs, following similar kinetics to those of high affinity receptor expression. This suggests that the 11 and 7 kb species carry information for high affinity insulin receptors, and that in U-937 cells the expression of this receptor subclass is primarily regulated at the mRNA level.
Leal
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MA
Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
Cabañas
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Rius
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Aller
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Calle
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C
D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000187:drug effects; D011972:Receptor, Insulin / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
D007328:Insulin; D012333:RNA, Messenger; D003907:Dexamethasone; D011972:Receptor, Insulin