Effects of Repeated LPS Infusion on Hematologic, Metabolic, and Intestinal Histology Parameters

Abstract

Objectives were to characterize effects of repeated lipopolysaccharide infusion on circulating metabolites, white blood cells, and intestinal histology in pigs. Ten crossbred female pigs (168 ± 2 kg) were reproductively synchronized and jugular catheterized. The experimental period, during the follicular phase of the estrous cycle, lasted 5 d and pigs were assigned to either control (CON; 3 mL i.v. saline; n=4) or lipopolysaccharide (LPS; 0.1 μg/kg BW LPS i.v.; Escherichia coli 055:B5 Sigma, St. Louis, Missouri; n=6) with treatments administered 4x/d at 0000, 0600, 1200, and 1800h. Each animal was limit‐fed 2.7 kg of feed once daily at 0600 h. Blood samples for metabolites and a complete blood count were obtained daily at 1730h. Rectal temperatures were measured 2x/d at 0530 and 1730h and condensed into daily averages. Animals were sacrificed on d 6 beginning at 0600h and segments of jejunum, ileum, and colon were collected and analyzed for morphology and were stained for myeloperoxidase (a measure of neutrophil infiltration). Circulating platelets were decreased 31% (P<0.01) and total white blood cell count tended to be decreased 10% (P=0.07) in LPS pigs relative to CON pigs. Lipopolysaccharide binding protein was increased 37% in LPS pigs relative to CON pigs (P=0.05) and was increased 60% on d 1 of the experiment relative to CON pigs (P = 0.02). There was a treatment by day interaction for neutrophils, lymphocytes, monocytes, and eosinophils where on d 1 only, neutrophils were increased 58% in LPS pigs relative to CON pigs (P<0.01) and lymphocytes, monocytes, and eosinophils were decreased by 61, 93, and 81%, respectively in LPS pigs relative to CON pigs (P<0.01 for all). Similar treatment by day differences in blood metabolites were observed where on d 1, insulin, blood urea nitrogen, β‐hydroxybutyric acid, and ionized calcium increased 36, 14, 13, and 7%, respectively, in LPS pigs relative to CON pigs (P=0.03, P=0.07, P=0.02, and P<0.01, respectively). There was no treatment by day interaction for blood glucose; however, it tended to be increased 6% in LPS pigs on d 1 relative to CON pigs (84 vs 79 mg/dL; P=0.08). Rectal temperature did not differ between the two treatments throughout the entire study (38.5 vs 38.6°C; P=0.71). In the jejunum, a tendency for reduced goblet cell area was observed (2.2 vs 5.6%; P=0.06) as well as an increase in myeloperoxidase stained area (1.03 vs 0.87%; P<0.01) in LPS pigs relative to CON pigs. No other differences in histological measurements were observed. In conclusion, LPS only altered metabolism on d 1 of the 5 d injection period. Platelets were the only measurement consistently affected throughout the 5 d. Jejunum was the only intestinal segment affected by repeated LPS exposure as determined by a tendency for reduced goblet cell area and an increase in myeloperoxidase stained area.