Mechanisms of membrane estrogen receptor- alpha -mediated rapid stimulation of Ca super(2+) levels and prolactin release in a pituitary cell line

• Published in: American journal of physiology: endocrinology and metabolism 2005-02, Vol.288 (2), p.E388-E397
• Main Authors: Bulayeva, Nataliya N, Wozniak, Ann L, Lash, LLeanne, Watson, Cheryl S
• Format: Article
• Language: English
• ISSN: 0193-1849; 1522-1555

The role of membrane estrogen receptor- alpha (mER alpha ) in rapid nongenomic responses to 17 beta -estradiol (E sub(2)) was tested in sublines of GH3/B6 rat prolactinoma cells selected for high (GH3/B6/F10) and low (GH3/B6/D9) mER alpha expression. E sub(2) elicited rapid, concentration-dependent intracellular Ca super(2+) concentration ([Ca super(2+)] sub(i)) increases in the F10 subline. Lack of inhibition by thapsigargin depletion of intracellular Ca super(2+) pools, together with abrogation of the response in Ca super(2+)-free medium, suggested an extracellular source of Ca super(2+) for this response. The participation of voltage-dependant channels in the E sub(2)-induced [Ca super(2+)] sub(i) increase was confirmed by the specific L-type Ca super(2+) channel inhibitor nifedipine. For comparison, the D9 mER alpha -depleted subline was insensitive to steroid action via this signaling mechanism. [Ca super(2+)] sub(i) elevation was correlated with prolactin (PRL) release in the F10 cell line in as little as 3 min. E sub(2) caused a much higher PRL release than KCl treatment (which caused maximal Ca super(2+) elevation), suggesting that secretion was also controlled by additional mechanisms. Participation of mER alpha in these effects was confirmed by the ability of E sub(2)-peroxidase (a cell-impermeable analog of E sub(2)) to cause these responses, blockage of the responses with the ER antagonist ICI 182 780, and the inability of the E sub(2) stereoisomer 17 alpha -E sub(2) to elicit a response. Thus rapid exocytosis of PRL is regulated in these cells by mER alpha signaling to specific Ca super(2+) channels utilizing extracellular Ca super(2+) sources and additional signaling mechanisms.