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)

• Published in: Neuroendocrinology
• Main Authors: Rousseau, Karine, Huang, Yung-Sen, Le Belle, Nadine, Vidal, Bernadette, Marchelidon, Jacques, Epelbaum, Jacques, Dufour, Sylvie
• Format: Article in Journal/Newspaper
• Language: English
• Published: S. Karger AG 1998
• Subjects: Anguilla anguilla
• Online Access: http://dx.doi.org/10.1159/000054327; https://www.karger.com/Article/Pdf/54327

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 (EC 50 0.75 n M) 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 sst 2 /sst 3 /sst 5 class rather than to the sst 1 /sst 4 class. Insulin-like growth factor 1 (IGF1) dose-dependently inhibited GH release (EC 50 0.03 n M) 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.