Submitted to: Journal of Fish Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2003
Publication Date: 8/1/2003
Citation: Peterson, B.C., Simpson, P.R., Cain, K.D., Hardy, R.H., Schelling, G.T., Ott, T.L. 2003. Effects of Administration of Somatostatin-14 and Immunoneutralization of Somatostatin on Endocrine and Growth Responses in Rainbow Trout (Oncorhynchus mykiss). Journal of Fish Biology. 63:506-522. Interpretive Summary: Somatostatin-14 is a hormone that negatively regulates endogenous levels of growth hormone (GH) in mammals and fish. The efficacy of neutralizing levels of SS-14 by passive and active immunization was tested in rainbow trout. In the first study, SS-14 at 5 and 50ng/g BW decreased levels of GH over time when compared to controls. In the second study, GH levels were increased in fish passively immunized against SS-14 when compared to controls. In the third study, overall growth rates and feed efficiency were not improved in fish actively immunized against SS-14. However, individual fish that responded to active immunization against SS-14 by producing antibody titers demonstrated improved growth rates and feed efficiency. These results indicated SS-14 regulates GH secretion similarly in rainbow trout as it does in mammals. This study also showed that active immunization against SS-14 could improve growth performance in rainbow trout but enhanced growth performance is dependent upon fish generating antibody titers against SS-14.
Technical Abstract: The objectives of this study were to examine (1) the effect of SS-14 on GH release; (2) the effect of passive immunization against SS-14 on GH release; and (3) the effect of active immunization against SS-14 on growth performance and levels of GH, IGF-I, and antibody titers in rainbow trout. In the first study, injection of SS-14 at 5 ng/g BW decreased (P < 0.05, cubic; r**2 = .54) levels of GH (1.5 = +/- 0.9 ng/ml vs. 6.6 +/- .6 ng/ml) over time when compared to controls. Somatostatin-14 at 50 ng/g BW also decreased (P = 0.064; quadratic; r**2 = .30) levels of GH (3.6 +/- 2.1 ng/ml vs. 6.6 +/- .6 ng/ml) over time compared to controls. In the second study, passive immunization against SS-14 (1:25 dose) increased (P = 0.10, cubic; r**2 = .12) levels of GH (11.0 +/- 4.8 ng/ml vs. 5.2 +/- 1.4 ng/ml) over time. Passively immunizing against SS (1:50 dose) increased (P < 0.05, cubic; r**2 = .10) levels of GH (8.2 +/- 2.3 ng/ml vs. 5.2 +/- 1.4 ng/ml) over time compared to controls. Overall, in the active immunization study there was no difference (P > 0.10) in specific growth rate (SGR) or feed conversion ratio (FCR) between the three treatment groups during the nine weeks of the study. However, only four of the fish immunized against SS-14 developed antibody titers against SS. Compared to controls, these fish exhibited a SGR of 0.89 +/- 0.09 vs. 0.56 +/- 0.09 and FCR of 0.8 +/- 0.04 vs. 1.2 +/- 0.05. In SS-14 immunized fish, levels of GH decreased (P < 0.05) by day 63 while levels of IGF-I increased (P < 0.05) by day 42 and 63. These results indicate the hypothalamic hormone SS-14 regulates GH secretion similarly in rainbow trout as it does in mammals. Active immunization against SS-14 could improve growth performance in rainbow trout but enhanced SGR and FCR is dependent upon generation of antibody titers.