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Announcement |
Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892-4510
Address all correspondence and requests for reprints to: Kevin J. Catt, M.D., Ph.D., Endocrinology and Reproduction Research Branch, Building 49, Room 6A-36, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892. E-mail: catt{at}helix.nih.gov.
ABSTRACT
Immortalized GnRH neurons (GT17) express receptors for estrogen [estrogen receptor-
and -ß(ER
and ERß)] and progesterone (progesterone receptor A) and exhibit positive immunostaining for both intracellular and plasma membrane ERs. Exposure of GT17 cells to picomolar estradiol concentrations for 560 min caused rapid, sustained, and dose-dependent inhibition of cAMP production. In contrast, treatment with nanomolar estradiol concentrations for 60 min increased cAMP production. The inhibitory and stimulatory actions of estradiol on cAMP formation were abolished by the ER antagonist, ICI 182,780. The estradiol-induced inhibition of cAMP production was prevented by treatment with pertussis toxin, consistent with coupling of the plasma membrane ER to an inhibitory G protein. Coimmunoprecipitation studies demonstrated an estradiol-regulated stimulatory interaction between ER
and G
i3 that was prevented by the ER antagonist, ICI 182,780. Exposure of perifused GT17 cells and hypothalamic neurons to picomolar estradiol levels increased the GnRH peak interval, shortened peak duration, and increased peak amplitude. These findings indicate that occupancy of the plasma membrane-associated ERs expressed in GT17 neurons by physiological estradiol levels causes activation of a Gi protein and modulates cAMP signaling and neuropeptide secretion.
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