Rapid and long-term effects of 17 beta-estradiol on PIP2-phospholipase C-specific activity of MCF-7 cells.
Activity of the enzyme phosphatidylinositol 4,5-bisphosphate phospholipase C (PIP2-PLC) was demonstrated in MCF-7 human breast cancer cell homogenate. The addition of 10(-9) M 17 beta-estradiol to the culture medium elicited in the cells two types of responses depending on the period of exposure. Enzyme activity was rapidly activated at 15 s of incubation. After 5 min, PIP2-PLC activity was inhibited, and this effect continued at least until 24 h of exposure to the hormone. When 17 beta-estradiol was added in vitro to the total homogenate of untreated cells, enzyme activity was stimulated in a dose-dependent manner. These findings indicate that 17 beta-estradiol induces early and long-term modifications of the phosphoinositide signal pathway in intact MCF-7 cells as well as in vitro. The rapidity of the early effect suggests a non-genomic action of estradiol.
Unité INSERM 224 affiliée CNRS, Faculté de Médecine Xavier Bichat, Paris, France.
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Graber
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Sumida
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Vallette
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Nunez
D002455:Cell Division; D004789:Enzyme Activation / Q000187:drug effects; D004958:Estradiol / Q000494:pharmacology*; D006801:Humans; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
D004958:Estradiol; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C