Growth hormone expression and secretion in pig pituitary and median eminence slices are not influenced by the VGF protein.
Body homeostasis is maintained by a complex system that involves the brain and the periphery via many circulating hormones. In recent years the VGF protein has been indicated as an important peptide affecting the regulation of body composition. We examined the effects of VGF on growth hormone (GH) expression and secretion in porcine pituitary slices, incubated alone (group 1) or with stalk median eminence (SME) (group 2). After 2 h (time 0), medium was removed and replaced with a fresh one; tissues were challenged with VGF (10(-6) M, 10(-8) M) alone or with ghrelin (10(-8) M) or growth hormone-releasing hormone (GHRH) (10(-8) M). Medium was replaced again 2 h (+2) and 6 h (+6) later. None of the VGF concentrations influenced GH secretion in either group; the association with GHRH or ghrelin appeared ineffective in influencing GH secretion as compared with the effects of GH mRNA expression and was not influenced by VGF treatments. The presence of SME had an additive effect on GH expression. Collectively, our results confirm previous findings on GH regulation; however, further investigations are needed to establish whether the modulation of GH secretion in the absence of nutrients involves the balance of GHRH/ghrelin receptors at pituitary levels. As for VGF, a crucial aspect to clarify is whether its lack of effects depends on our experimental conditions or, alternatively, it is not effective at all.
Saleri
Roberta
R
Department of Animal Production, Veterinary Biotechnology and Food Safety, Section of Veterinary Physiology, University of Parma, Parma, Italy. roberta.saleri@unipr.it
Cavalli
Valeria
V
Grasselli
Francesca
F
Tamanini
Carlo
C
D000704:Analysis of Variance; D000818:Animals; D015139:Blotting, Southern / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D015870:Gene Expression / Q000187:drug effects*; D054439:Ghrelin; D013006:Growth Hormone / Q000235:genetics / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D007118:Immunoassay / Q000379:methods; D066298:In Vitro Techniques; D008473:Median Eminence / Q000187:drug effects*; D009479:Neuropeptides / Q000494:pharmacology*; D036361:Peptide Hormones / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013552:Swine
D054439:Ghrelin; D009479:Neuropeptides; D036361:Peptide Hormones; D012333:RNA, Messenger; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone