Integrated adrenal, somatotropic, and immune responses of growing pigs to treatment with lipopolysaccharide

The objective of this research was to provide an integrated look at systemi c adrenal, somatotropic, and immune responses of growing pigs to challenge with lipopolysaccharide (LPS). Weaned pigs were challenged intraperitoneall y with 100 mu g/kg BW of LPS or sterile saline, and rectal temperature and blood data were collected for 72 h. Daily feed intake also was monitored. P lasma was analyzed for concentrations of cortisol, tumor necrosis factor al pha (TNF alpha), the acute phase protein haptoglobin, growth hormone (GH), insulin-like growth factor I (IGF-I), and prostaglandin E-2 (PGE(2)). As ex pected, LPS decreased feed intake, stimulated a febrile response, and activ ated the hypothalamic-pituitary-adrenal (HPA) axis as demonstrated by incre ased cortisol levels. Cortisol reached maximum elevation 2 h after treatmen t (P < .001) and remained elevated through 12 h (P < .001). Circulating TNF a was increased by LPS at 2 and 4 h after treatment (P < .001), and an appa rent (not statistically significant) increase in haptoglobin also occurred in challenged animals. The LPS injection suppressed IGF-I by 2 h following treatment (P < .01), and circulating IGF-I remained reduced relative to con trols through 44 h. Overall, GH was increased in LPS-treated pigs (P < .05) , although the treatment x time interaction was not significant. Plasma PGE (2) was increased transiently at 2 h (P < .05) and then subsequently suppre ssed at 4, 8, and 12 h following LPS (P < .05). This study provides a compr ehensive view of systemic effects of LPS on components of the HPA, growth, and immune axes. In addition, these are the first data to document changes in circulating PGE(2) in unrestrained animals during the early hours of the acute phase response to LPS.