title: Osmotic regulation of estrogen receptor-beta in rat vasopressin and oxytocin neurons.
abstract: The vasopressin (VP) magnocellular neurosecretory cells (MNCs) in the supraoptic and paraventricular (PVN) nuclei are regulated by estrogen and exhibit robust expression of estrogen receptor (ER)-beta. In contrast, only approximately 7.5% of oxytocin (OT) MNCs express ER-beta. We examined the osmotic regulation of ER-beta mRNA expression in MNCs using quantitative in situ hybridization histochemistry. Hyper-osmolality induced via 2% hypertonic saline ingestion significantly decreased, whereas sustained hypo-osmolality induced via d-d-arginine VP and liquid diet increased ER-beta mRNA expression in MNCs (p < 0.05). Thus, the expression of ER-beta mRNA correlated inversely with changes in plasma osmolality. Because hyper-osmolality is a potent stimulus for VP and OT release, this suggests an inhibitory role for ER-beta in MNCs. Immunocytochemistry demonstrated that the decrease in ER-beta mRNA was translated into depletion of receptor protein content in hyper-osmotic animals. Numerous MNCs were positive for ER-beta in control animals, but they were virtually devoid of ER-beta-immunoreactivity (IR) in hyper-osmotic animals. The osmotically induced decrease in ER-beta expression was selective for MNCs because ER-beta-IR remained unaltered in PVN parvocellular neurons. Plasma estradiol and testosterone were not correlated with ER-beta mRNA expression after osmotic manipulation, suggesting that ER-beta expression was not driven by ligand availability. Expression of FOS-IR in MNCs with attenuated ER-beta-IR, and the absence of FOS-IR in parvocellular neurons that retain ER-beta-IR suggest a role for neuronal activation in the regulation of ER-beta expression in MNCs. Thus, osmotic modulation of ER-beta expression in MNCs may augment or attenuate an inhibitory effect of gonadal steroids on VP release.
authors.affiliation: Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
authors.forename: Suwit J
authors.initials: SJ
authors.lastname: Somponpun
authors.forename: Celia D
authors.initials: CD
authors.lastname: Sladek
mesh_terms: D000818:Animals; D001810:Blood Volume / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D047629:Estrogen Receptor beta; D006400:Hematocrit; D006728:Hormones / Q000097:blood / Q000502:physiology; D006955:Hypernatremia / Q000503:physiopathology; D007010:Hyponatremia / Q000503:physiopathology; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D010121:Oxytocin / Q000097:blood / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012965:Sodium Chloride / Q000378:metabolism; D013495:Supraoptic Nucleus / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D014667:Vasopressins / Q000097:blood / Q000378:metabolism*; D014882:Water-Electrolyte Balance / Q000502:physiology; D014883:Water-Electrolyte Imbalance / Q000503:physiopathology
chemical_list: D047629:Estrogen Receptor beta; D006728:Hormones; D011960:Receptors, Estrogen; D014667:Vasopressins; D012965:Sodium Chloride; D010121:Oxytocin