title: Estradiol inhibits depolarization-evoked exocytosis in PC12 cells via N-type voltage-gated calcium channels.
abstract: Fast neuromodulatory effects of 17-β-estradiol (E2) on cytosolic calcium concentration ([Ca(2+)](i)) have been reported in many cell types, but little is known about its direct effects on vesicular neurotransmitter secretion (exocytosis). We examined the effects of E2 on depolarization-evoked [Ca(2+)](i) in PC12 cells using fluorescence measurements. Imaging of [Ca(2+)](i) with FURA-2 revealed that depolarization-evoked calcium entry is inhibited after exposure to 10 nM and 10 μM E2. Calcium entry after exposure to 50 μM E2 decreases slightly, but insignificantly. To relate E2-induced changes in [Ca(2+)](i) to functional effects, we measured exocytosis using amperometry. It was observed that E2 in some cells elicits exocytosis upon exposure. In addition, E2 inhibits depolarization-evoked exocytosis with a complex concentration dependence, with inhibition at both physiological and pharmacological concentrations. This rapid inhibition amounts to 45% at a near physiological level (10 nM E2), and 50% at a possible pharmacological concentration of 50 μM. A small percentage (22%) of cells show exocytosis during E2 exposure ("Estrogen stimulated"), thus vesicle depletion could possibly account (at least partly) for the E2-induced inhibition of depolarization-evoked exocytosis. In cells that do not exhibit E2-stimulated release ("Estrogen quiet"), the E2-induced inhibition of exocytosis is abolished by a treatment that eliminates the contribution of N-type voltage-gated calcium channels (VGCCs) to exocytosis. Overall, the data suggest that E2 can act on N-type VGCCs to affect secretion of neurotransmitters. This provides an additional mechanism for the modulation of neuronal communication and plasticity by steroids.
authors.affiliation: Department of Chemistry, The Pennsylvania State University, 104 Chemistry Research Building, University Park, PA 16802, USA.
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Adams
authors.forename: Marc M
authors.initials: MM
authors.lastname: Maxson
authors.forename: Lisa
authors.initials: L
authors.lastname: Mellander
authors.forename: Remco H S
authors.initials: RH
authors.lastname: Westerink
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Ewing
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology*; D005089:Exocytosis / Q000187:drug effects*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects*; D016716:PC12 Cells; D051381:Rats
chemical_list: D020864:Calcium Channels, N-Type; D004958:Estradiol; D002118:Calcium