title: Effects of GH on immune and endocrine responses of channel catfish challenged with Edwardsiella ictaluri.
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.
authors.affiliation: USDA/ARS Catfish Genetics Research Unit, Thad Cochran National Warmwater Aquaculture Center, PO Box 38, Stoneville, MS 38776, USA. bpeterson@ars.usda.gov
authors.forename: Brian C
authors.initials: BC
authors.lastname: Peterson
authors.forename: Brian C
authors.initials: BC
authors.lastname: Small
authors.forename: Lanie
authors.initials: L
authors.lastname: Bilodeau
mesh_terms: D000818:Animals; D002417:Cattle; D020610:Edwardsiella ictaluri / Q000472:pathogenicity*; D004756:Enterobacteriaceae Infections / Q000276:immunology / Q000401:mortality / Q000662:veterinary*; D005393:Fish Diseases / Q000276:immunology* / Q000401:mortality; D013006:Growth Hormone / Q000494:pharmacology*; D007059:Ictaluridae / Q000276:immunology* / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D009113:Muramidase / Q000097:blood; D012333:RNA, Messenger / Q000032:analysis; D011986:Receptors, Somatotropin / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D051198:Toll-Like Receptor 5 / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D011994:Recombinant Proteins; D051198:Toll-Like Receptor 5; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D009113:Muramidase