Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 1997
Publication Date: N/A
Technical Abstract: It is not known whether the proinflammatory cytokine interleukin-6 (IL-6) is fully induced in neonates exposed to bacterial infections. This study evaluated tissue-specific expression of IL-6 mRNA in spleen, liver, thymus, pituitary gland, and hypothalamus following a peripheral injection of lipo- polysaccharide (LPS) from E. coli (150 ug/kg) in 1, 21, and 28 d old pigs. For each pig injected with LPS one littermate of the same sex was injected with saline as a control. At 3 h postinjection, pigs were sacrificed and tissue samples were collected. Slot blotting and scanning densitometry method was used to quantify IL-6 mRNA. All values were normalized to beta- actin and expressed as relative units. Overall effect of LPS (P = 0.0001) was highly significant, tissue differences (P = 0.0001), and effect of age (P = 0.0233). Although LPS stimulated increased IL-6 mRNA expression in all tissues, the highest mRNA expression was detected in the pituitary gland. The most significant general age difference in mRNA induction in response to LPS in pigs was observed between 1 and 28 d of age (P = 0.0064). IL-6 mRNA expression in 1 vs. 28 d old LPS-injected pigs was 0.889 +/ 0.237 vs. 1.187 +/ 0.268 in the spleen, 2.915 +/ 0.921 vs. 3.569 +/ 1.312 in the liver, 3.989 +/ 1.226 vs. 6.677 +/ 2.217 in the thymus, 5.299 +/ 0.589 vs. 12.375 +/ 4.150 in the pituitary gland, and 3.663 +/ 0.514 vs. 11.762 +/ 5.118 relative units in the hypothalamus, respectively. Results indicate that, although neonatal pigs respond to bacterial LPS by increased expression of IL-6 mRNA as early as 1 d of age, level of expression is relatively low at this age. An undeveloped acute phase response could contribute to high mortality and morbidity due to bacterial infections occurring during the first few days after birth.