Submitted to: American Society of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: April 22, 2005
Publication Date: July 1, 2005
Citation: Li, C., Elsasser, T.H., Kahl, S., Carbaugh, D. 2005. Temporal response of signal transduction elements during endotoxin (LPS) challenge in cattle liver cells: Effects of growth hormone treatment [abstract]. Journal of Animal Science. 83(suppl 1):8. Technical Abstract: Exogenous growth hormone (GH) treatment has been explored as one potential adjunct for management of catabolic processes that further challenge the host response to infection stress. Few definitive studies in cattle, if any, have addressed NO production as affected by GH treatment prior to the onset of immune challenge as well as signal transduction pathways that involved. We examined the expression of inducible nitric oxide synthase (iNOS) and the activities of potential signal transduction pathway elements in cattle liver cells in response to LPS challenge and the modification of these responses by daily treatment with recombinant GH prior to Lipopolysaccharide (LPS) challenge (LPS; 3.0 µg/kg BW, i.v. bolus, E. coli 055:B5). Animals (n=24) were divided into GH- and nonGH-treatment groups (n=12/group, GH-treated (recombinant bovine GH, Monsanto Inc., 4 St. Louis, MO; 0.1 mg/kg BW, im, daily for 12 days, no LPS) in a factorial arrangement of GH treatment (+/-) and biopsy sampling time. In responses to LPS challenge the level of iNOS increased significantly (P < 0.001) in first three hrs and maintained at higher level thereafter to 24 hrs. In GH treated animals, the level of iNOS protein were increased at zero, three and 6 hr and significantly higher than that in non-GH treated animals (P < 0.001). GH treatment sitmulates the phosphorylation of Akt/PKB. Family of mitogen-activated protein kinases (MAPK), Erk, SAPK/JUK and p38 showed very different patterns of response. When the temporal profile of phospho-Erk only response to LPS in GH treated animals (P < 0.001), phospho-SAPK/JUN response to LPS in both GH treated and non GH treated animals with significant higher level of phosphorylation (P < 0.001) in GH treated group. P38MAPK showed no temporal response to LPS in both groups, the possible mechanism of the augmentation of LPS-induced NO production by GH is discussed.