Orexin-B modulates luteinizing hormone and growth hormone secretion from porcine pituitary cells in culture.
To test the hypothesis that orexin-B acts directly on the anterior pituitary to regulate LH and growth hormone (GH) secretion, anterior pituitary cells from prepuberal gilts were studied in primary culture. On day 4 of culture, 10(5) cells/well were challenged with 0.1, 10 or 1000 nM GnRH; 10, 100 or 1000 nM [Ala15]-hGRF-(1-29)NH2 or 0.1, 1, 10 or 100 nM, orexin-B individually or in combinations with 0.1 and 1000 nM GnRH or 10 and 1000 nM GRF. Secreted LH and GH were measured at 4 h after treatment. Basal LH and GH secretion (control; n = 6 pigs) was 183 +/- 18 and 108 +/- 4.8 ng/well, respectively. Relative to control at 4 h, all doses of GnRH and GRF increased (P < 0.0001) LH and GH secretion, respectively. All doses of orexin-B increased (P < 0.01) LH secretion, except for the 0.1 nM dose. Basal GH secretion was unaffected by orexin-B. Addition of 1, 10 or 100 nM orexin-B in combinations with 0.1 nM GnRH increased (P < 0.001) LH secretion compared to GnRH alone. Only 0.1 nM (P = 0.06) and 100 nM (P < 0.001) orexin-B in combinations with 1000 nM GnRH increased LH secretion compared to GnRH alone. All doses of orexin-B in combination with 1000 nM GRF suppressed (P < 0.0001) GH secretion compare to GRF alone, while only 0.1 nM orexin-B in combination with 10 nM GRF suppressed (P < 0.01) GH secretion compared to GRF. These results indicate that orexin may directly modulate LH and GH secretion at the level of the pituitary gland.
Barb
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USDA, ARS, Animal Physiology Research Unit, Russell Research Center, P.O. Box 5677, Athens, GA 30604-5677, USA. rbarb@saa.ars.usda.gov
Matteri
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D000818:Animals; D002478:Cells, Cultured; D007987:Gonadotropin-Releasing Hormone / Q000008:administration & dosage; D013006:Growth Hormone / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D007986:Luteinizing Hormone / Q000378:metabolism*; D009479:Neuropeptides / Q000008:administration & dosage / Q000494:pharmacology*; D000068797:Orexins; D010903:Pituitary Gland, Anterior / Q000187:drug effects* / Q000378:metabolism*; D013552:Swine
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D013006:Growth Hormone