Estradiol modulation of growth hormone secretion in the ewe: no growth hormone-releasing hormone neurons and few somatotropes express estradiol receptor alpha.
Evidence suggests that estrogen modulates growth hormone (GH) release and that GH plays an important role in follicular and ovulatory processes. How estradiol affects GH secretion is unclear. Having verified that there is a coincident surge of GH at the time of the preovulatory LH surge, immunocytochemical studies incorporating high-temperature antigen retrieval were used to determine whether GH-releasing hormone (GHRH) neurons, somatotropes, or both, expressed estrogen receptor alpha (ER), in the ewe. Although GHRH neurons were surrounded by many ER cells, they did not express immunocytochemically detectable ERs. In contrast to gonadotropes, in which the majority expressed ERs, few somatotropes were estrogen receptive. These data suggest that estrogen does not act directly on GHRH neurons to influence GH secretion, and any direct effect on pituitary GH release, through the ERalpha, may be small.
Scanlan
Niamh
N
Department of Clinical Veterinary Science, University of Bristol, Langford, Bristol BS40 5DU, United Kingdom. n.scanlan@bristol.ac.uk
Skinner
Donal C
DC
D000818:Animals; D000918:Antibody Specificity; D004958:Estradiol / Q000378:metabolism* / Q000494:pharmacology*; D047628:Estrogen Receptor alpha; D005260:Female; D013006:Growth Hormone / Q000097:blood; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D007150:Immunohistochemistry; D007986:Luteinizing Hormone / Q000097:blood; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010052:Ovariectomy; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism; D011960:Receptors, Estrogen / Q000096:biosynthesis*; D012756:Sheep
D047628:Estrogen Receptor alpha; D011960:Receptors, Estrogen; D004958:Estradiol; D007986:Luteinizing Hormone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone