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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.
R Graber, and
C Sumida, and
G Vallette, and
E A Nunez
November 1992,
Cancer research,
R Graber, and
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May 1988,
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June 1989,
Journal of steroid biochemistry,
R Graber, and
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E A Nunez
January 1992,
Breast cancer research and treatment,
R Graber, and
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February 1989,
Journal of steroid biochemistry,
R Graber, and
C Sumida, and
G Vallette, and
E A Nunez
October 1987,
Cancer research,
R Graber, and
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September 1994,
Steroids,
R Graber, and
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August 1995,
Steroids,
R Graber, and
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September 1985,
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R Graber, and
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July 1999,
Biochemical and biophysical research communications,
