Long-term inhibitory effects of somatostatin and insulin-like growth factor 1 on growth hormone release by serum-free primary culture of pituitary cells from European eel (Anguilla anguilla).
To investigate the ability of hypothalamic and peripheral factors to directly regulate growth hormone (GH) release in a primitive teleost, the European eel (Anguilla anguilla L.), we used primary cultures of dispersed pituitary cells. When cultured for 12 days in a serum-free medium, pituitary cells continuously released large amounts of GH, which exceeded the initial cellular content. Somatotropin-release inhibiting hormone (SRIH-14) dose-dependently inhibited GH release (EC50 0.75 nM) up to a maximal inhibitory effect of 95%. No desensitization of somatotropes to SRIH was observed over the 12 days of culture. Use of receptor subtype-selective SRIH agonists suggests the existence on eel somatotropes of SRIH receptor(s) related to the mammalian sst2/sst3/sst5 class rather than to the sst1/sst4 class. Insulin-like growth factor 1 (IGF1) dose-dependently inhibited GH release (EC50 0.03 nM) up to a maximal inhibitory effect of 85%, without desensitization. IGF1 and IGF2 were equipotent in inhibiting GH release, whereas insulin was 1,000 times less active, suggesting the implication of a receptor related to the mammalian IGF type 1 receptor. These results indicate that eel somatotropes are active in vitro without any specific additional factors, and suggest the existence of a dominant inhibitory control of GH release in vivo. Two potential candidates for this chronic negative regulation are a neurohormone, SRIH and a circulating factor, IGF1. These data underline the early evolutionary origin of the molecular and functional SRIH-GH-IGF1 neuroendocrine axis in vertebrates.
Rousseau
K
K
Laboratoire de Physiologie Générale et Comparée, Muséum National d'Histoire Naturelle, URA 90 CNRS, Paris, France.
Huang
Y S
YS
Le Belle
N
N
Vidal
B
B
Marchelidon
J
J
Epelbaum
J
J
Dufour
S
S
D000811:Anguilla / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D013006:Growth Hormone / Q000378:metabolism*; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D012636:Secretory Rate / Q000187:drug effects; D013004:Somatostatin / Q000819:agonists / Q000494:pharmacology*; D013997:Time Factors
D016895:Culture Media, Serum-Free; D013004:Somatostatin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone