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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATION OF NUTRITIONAL, GENETIC AND PHYSIOLOGICAL APPROACHES TO IMPROVE PRODUCTION EFFICIENCY OF RAINBOW TROUT Title: Bovine Growth Hormone Treatment Increased Igf-I in Circulation and Induced the Production of a Specific Immune Response in Rainbow Trout (Oncorhynchus Mykiss)

Authors
item Biga, P. - UNIV OF IDAHO, MOSCOW
item Peterson, Brian
item Schelling, G. - UNIV OF IDAHO, MOSCOW
item Overturf, Kenneth
item Hardy, R. - UNIV OF IDAHO, HAGERMAN
item Cain, K. - UNIV OF IDAHO, MOSCOW
item Ott, T. - UNIV OF IDAHO, MOSCOW

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2005
Publication Date: April 22, 2005
Citation: Biga, P.R., Peterson, B.C., Schelling, G.T., Hardy, R.W., Cain, K.D., Overturf, K., Ott, T.L. (2005) Bovine growth hormone treatment increased IGF-I in circulation and induced the production of a specific immune response in rainbow trout (Oncorhynchus mykiss), Aquaculture 246, 437-445.

Interpretive Summary: Recombinant bovine growth hormone (rbGH) increases growth rates in rainbow trout and this response is thought to be under the same control as it is in mammals. However, the mechanisms regulating fish muscle growth are poorly understood. Therefore, an experiment was conducted to examine the effects of rbGH on growth-related hormones in rainbow trout. Rainbow trout received two injections of rbGH or a control substance. Blood samples were collected and assayed for rainbow trout growth hormone and other related factors. As expected, rbGH levels increased in circulation 12 h after treatment and continued to increase from after treatment. Unexpectedly, levels of rbGH detected at day 28, 7 days after the second injection, were lower than those at day 7. Corresponding to this observation, anti-rbGH antibodies were detectable in serum from treated fish at day 28, but not at day 7. We suggest that the low levels of rbGH detected at day 28 were due to increased clearance of rbGH caused by the anti-rbGH antibodies. Treated fish also exhibited increased serum growth factor levels following rbGH injection, while endogenous trout GH did not change. These results suggest that the endogenous negative feedback control loop described in mammals is not activated by rbGH in rainbow trout, as trout GH was unaffected by increased circulating rbGH. To our knowledge, this is the first report demonstrating specific antibody production following an exogenous rbGH injection in fish.

Technical Abstract: Recombinant bovine growth hormone (rbGH) increases growth rates in rainbow trout and this response is thought to be under the control of the GH-IGF axis, as it is in mammals. However, the mechanisms regulating fish muscle growth are poorly understood. Therefore, an experiment was conducted to examine the effects of rbGH on growth-related hormones in rainbow trout. Rainbow trout (550+10 g) received an intraperitoneal injection of rbGH (120 'g g-1 BW) or vehicle on days 0 and 21. Blood samples were collected on days 0, 0.5, 1, 3, 7, and 28 and assayed for rainbow trout growth hormone (tGH), rbGH and IFG-I. As expected, rbGH levels increased in circulation 12 h after treatment and continued to increase from day 0 to day 7 after treatment. Unexpectedly, levels of rbGH detected at day 28, 7 days after the second injection, were lower than those at day 7. Corresponding to this observation, anti-rbGH antibodies were detectable in serum from treated fish at day 28, but not at day 7. We suggest that the low levels of rbGH detected at day 28 were due to increased clearance of rbGH caused by the anti-rbGH antibodies. Treated fish also exhibited increased serum IGF-I levels following rbGH injection, while endogenous tGH did not change. These results suggest that the endogenous negative feedback control loop described in mammals is not activated by rbGH in rainbow trout, as tGH was unaffected by increased circulating rbGH and IGF-I. However, consistent with previous reports, rbGH does increase circulating IGF-I over time and rbGH is detectable throughout the 3-week injection period. To our knowledge, this is the first report demonstrating specific antibody production following an exogenous rbGH injection in fish.

Last Modified: 10/22/2014
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