Impact of environmental temperature on response of neonatal pigs to an endotoxin challenge

Objective-To evaluate the effect of various environmental temperatures (ET) on the ability of neonatal pigs to cope with an endotoxin challenge. Animals-28 crossbred male pigs that were 24 hours old. Procedure-At 24 hours of age, pigs were placed in environmentally controlle d chambers maintained at 18 or 34 C (14 pigs/ET). Rectal temperatures (RT) were recorded at 15-minute intervals for 3 hours following an IP injection of 0.9% NaCl (7 control pigs/ET) or lipopolysaccharide (LPS; 150 mug/kg of body weight; 7 LPS-treated pigs/ET). Tissue specimens and blood samples wer e collected following the 3-hour challenge period. Results-LPS-treated pigs exposed to 18 C had a period of hypothermia wherea s RT for LPS-treated pigs at 34 C did not differ from control pigs. The LPS -treated pigs maintained at 18 C lost the most body weight during the 3-hou r period and also had the greatest increase in serum cortisol concentration . Serum prolactin (PRL) concentration was decreased in pigs at 18 C, compar ed with pigs at 34 C, Challenge with LPS resulted in an increase in serum P RL concentration at 18 C but had no effect on serum PRL at 34 C. Challenge with LPS resulted in an increase in expression of tumor necrosis factor-alp ha, interleukin-1 beta, and interleukin-6 receptor mRNA in the hypothalamus . Conclusions and Clinical Relevance-Exposure to a cold ET can inhibit the ab ility of neonatal pigs to cope with an exogenous endotoxin challenge. When combined, cold stress and exposure to exogenous endotoxin induces a rapid a nd potentially dangerous loss of body temperature in neonatal pigs.