Growth hormone (GH) has been shown to contribute to the seawater (SW) adaptability of euryhaline fish both directly and indirectly through insulin-like growth factor-1 (IGF-1). This study examined the role of somatostatin-14 (SS-14), a potent inhibitor of GH, on the GH-IGF-1 axis and seawater adaptation. Juvenile rainbow trout (Oncorhynchus mykiss) were injected intraperitoneally with SS-14 or saline and transferred to 20??ppt seawater. A slight elevation in plasma chloride levels was accompanied by significantly reduced gill Na+, K+-ATPase activity in SS-14-treated fish compared to control fish 12??h after SW transfer. Seawater increased hepatic mRNA levels of GH receptor 1 (GHR 1; 239%), GHR 2 (48%), and IGF-1 (103%) in control fish 12??h after transfer. Levels of GHR 1 (155%), GHR 2 (121%), IGF-1 (200%), IGF-1 receptor A (IGFR1A; 62%), and IGFR1B (157%) increased in the gills of control fish 12??h after transfer. SS-14 abolished or attenuated SW-induced changes in the expression of GHR, IGF-1, and IGFR mRNAs in liver and gill. These results indicate that SS-14 reduces seawater adaptability by inhibiting the GH-IGF-1 axis. ?? 2007 Elsevier B.V. All rights reserved.
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Effects of somatostatin on the growth hormone-insulin-like growth factor axis and seawater adaptation of rainbow trout (Oncorhynchus mykiss)