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.