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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 controlled 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 microg/kg of body weight; 7 LPS-treated pigs/ET). Tissue specimens and blood samples were collected following the 3-hour challenge period.


RESULTS
LPS-treated pigs exposed to 18 C had a period of hypothermia whereas 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-hour period and also had the greatest increase in serum cortisol concentration. Serum prolactin (PRL) concentration was decreased in pigs at 18 C, compared with pigs at 34 C. Challenge with LPS resulted in an increase in serum PRL 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-alpha, interleukin-1 beta, and interleukin-6 receptor mRNA in the hypothalamus.


CONCLUSIONS AND CLINICAL RELEVANCE
Exposure to a cold ET can inhibit the ability of neonatal pigs to cope with an exogenous endotoxin challenge. When combined, cold stress and exposure to exogenous endotoxin induces a rapid and potentially dangerous loss of body temperature in neonatal pigs.