Abstract
The role of nongenomic action of estrogens on elicited catecholamine secretion and exocytosis kinetics was studied in perfused rat adrenals and in cultured bovine chromaffin cells. 17β-Estradiol as well as the estrogen receptor modulators raloxifene and LY117018, but not 17α-estradiol, inhibited at the micromolar range the catecholamine output elicited by acetylcholine or high potassium. However, these agents failed to modify the secretion elicited by high Ca2+ in glands treated with the ionophore A-23187 (calcimycin), suggesting that estrogens did not directly act on the secretory machinery. At the single cell level, estrogens modified the kinetics of exocytosis at nanomolar range. All of the drugs tested except 17α-estradiol produced a profound slowing down of the exocytosis as measured by amperometry. LY117018 also reduced the granule content of catecholamines. 17β-Estradiol reduced the intracellular free Ca2+ but only at micromolar concentrations, whereas nanomolar concentrations increased the cAMP levels. These effects were reproduced with the nonpermeable drug 17β-estradiol-horseradish peroxidase and antagonized with nanomolar concentrations of the antiestrogen ICI 182,780 (fulvestrant). Our data suggest the presence of membrane sites that regulate both the exocytotic phenomenon and the total catecholamine release with high and low affinity, respectively.
Footnotes
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This work was supported in part by grants from Spanish Ministerio de Ciencia y Tecnologı́a (PB97-1483 and BFI2001-3531), Gobierno de Canarias, and Fondo Europeo de Desarrollo Regional (1FD97-1065-C03-01). We also received partial financial support from Eli Lilly & Co. SA (Madrid), Zeneca Farma, SA (Madrid), and Compania Espanola de Petróleos Sociedad Anonima (Tenerife). J.D.M. was the recipient of a fellowship from Instituto Tecnológico de Canarias, A.M. from Spanish Ministerio de Ciencia y Tecnologı́a, and J.F.G. from Consejerı́a de Educación del Gobierno de Canarias. A poster from this paper was presented at the 11th International Symposium on Chromaffin Cell Biology (San Diego, CA).
- Abbreviations:
- ACh
- acetylcholine
- CA
- catecholamine
- [Ca2+]c
- cytosolic calcium concentration
- DMPP
- 1,1-dimethyl-4-phenylpiperazinium
- HRP
- horseradish peroxidase
- IBMX
- 3-isobutyl-1-methylxanthine
- ICI 182,780
- fulvestrant
- A-23187
- calcimycin
- Received November 2, 2001.
- Accepted February 1, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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