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ARS Home » Southeast Area » Stoneville, Mississippi » Warmwater Aquaculture Research Unit » Research » Publications at this Location » Publication #199964
Title: Effects of GH on Immune and Endocrine Responses of Channel Catfish Challenged with Edwardsiella ictaluri

Author
item Peterson, Brian
item Small, Brian
item Bilodeau, Lanie

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2006
Publication Date: 1/1/2007
Citation: Peterson, B.C., Small, B.C. 2007. Effects of GH on Immune and Endocrine Responses of Channel Catfish Challenged with Edwardsiella ictaluri. Comparative Biochemistry and Physiology A 146:47-53.

Interpretive Summary: The effects of growth hormone (GH) on immune and endocrine responses to channel catfish exposed to Edwardsiella ictaluri (E. ictaluri) were examined. Catfish treated with GH gained 19% more weight than control fish. Catfish that were given GH and exposed with E. ictaluri experienced similar mortality as Control-Exposed fish. Plasma activity of lysozyme was higher GH-Exposed fish. Compared to day 0 controls (Non-exposed fish), insulin like growth factor I (IGF-I) levels decreased in both treatments of challenged fish. Abundance of GH receptor (GHR) mRNA tended to decrease in liver of exposed fish while toll like receptor 5 (TLR5) mRNA increased in the liver. An increase in lysozyme may suggest GH enhances a nonspecific immune response. A decrease in GHR mRNA and plasma IGF-I suggests a downregulation of the axis that regulates growth in response to disease. The increase in TLR5 mRNA suggests that TLR5 may play a role in host response to bacterial challenge. While GH may play a stimulatory role to increase lysozyme levels, there was no apparent effect of GH on mortality to E. ictaluri.

Technical Abstract: The effects of GH on immune and endocrine responses to channel catfish challenged with the bacterium Edwardsiella ictaluri were examined. Catfish (11.7 +/- 1.0 g) treated with recombinant bovine growth hormone (rbGH) and challenged with E. ictaluri experienced similar mortality as Control-Exposed fish. Plasma activity of lysozyme was higher (P < 0.01) in rbGH-Exposed fish. Compared to day 0 controls (Non-exposed fish), IGF-I levels decreased (P < 0.05) in challenged fish while levels were similar (P > 0.10) between treatments. Abundance of GH receptor (GHR) mRNA tended to decrease (P = 0.055) in liver of challenged fish while toll like receptor 5 (TLR5) mRNA increased (P < 0.05) in liver compared to d 0 controls. An increase in lysozyme may suggest GH enhances a nonspecific immune response. A decrease in GHR mRNA and plasma IGF-I suggests a downregulation of the somatotropic axis in response to disease. The increase in TLR5 mRNA suggests that TLR5 may play a role in host response to bacterial challenge. While exogenous rbGH may play a stimulatory role to increase lysozyme levels, there was no apparent effect of rbGH on mortality to E. ictaluri.