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Department of Animal Health, Welfare and Nutrition, Faculty of Agricultural Sciences, University of Aarhus, 8830 Tjele, Denmark
1 Corresponding author: ChristineM.Rontved{at}agrsci.dk
A minimally invasive liver biopsy technique was tested for its applicability to study the hepatic acute phase response (APR) in dairy cows with Escherichia coli lipopolysaccharide (LPS)-induced mastitis. The hepatic mRNA expression profiles of the inflammatory cytokines, tumor necrosis factor 
(TNF-), IL-1β, IL-6, and IL-10, and the acute phase proteins serum amyloid A isoform 3 (SAA3), haptoglobin (Hp), and 1-acid glycoprotein (AGP) were determined by real-time reverse transcription-PCR. Fourteen primiparous cows in mid lactation were challenged with 200 µg of LPS (n = 8) or NaCl solution (n = 6) in 1 front quarter. Six repeated liver biopsies were collected at –22, 3, 6, 9, 12, and 48 h relative to LPS challenge in 4 LPS-infused cows and 3 NaCl-infused cows. The remaining cows had 3 liver biopsies taken at –22, 9, and 48 h. Production data and clinical signs were recorded and white blood cell counts and somatic cell counts (SCC) were analyzed to investigate the effect of repeated liver biopsies and verify the LPS model. Plasma concentrations of TNF-, SAA3, Hp, and AGP were determined for comparison with the liver expression data. Repeated liver biopsies had no effects on the production data, clinical signs, or APR of dairy cows. Compared with the NaCl-infused cows the LPS-infused cows responded to the LPS treatment by increased body temperature (38.6 ± 0.1 vs. 39.4 ± 0.1°C), short-term leukopenia followed by leukocytosis (6.44 ± 0.4 vs. 5.69 ± 0.3 x 106 cells/mL), an increased SCC (log10 2.1 ± 0.1 vs. log10 2.8 ± 0.1 x 103 cells/mL), heart rate (76 ± 1 vs. 93 ± 1 beats/min), and respiratory rate (32 ± 2 vs. 36 ± 1 breaths/min) in the acute phase of the disease. The LPS treatment upregulated the hepatic expression of TNF- (103 ± 24 vs. 255 ± 18 units), IL-1β (37 ± 23 vs. 296 ± 18 units), IL-6 (8 ± 17 vs. 122 ± 12 units), and IL-10 (130 ± 66 vs. 541 ± 50 units), and SAA3 (64 ± 36 vs. 128 ± 28 units) and Hp (9 ± 82 vs. 762 ± 65 units) reaching maximum levels at 3 to 6 h and 9 to 12 h postinfusion, respectively. Plasma concentrations of TNF- (nondetectable vs. 1.9 ± 0.3 ng/mL), SAA (19.8 ± 19.4 vs. 149.7 ± 15.5 µg/mL) and Hp (71.4 ± 143.7 vs. 1,013.8 ± 111.5 µg/mL) were elevated in the LPS-infused cows at 4 to 12 h, 8 to 120 h, and 24 to 120 h postinfusion, respectively. The hepatic expression of AGP and the AGP plasma concentration remained unaltered in LPS-induced cows. In conclusion, a minimally invasive liver biopsy technique can be used for studying the hepatic APR in diseased cattle. Lipopolysaccharide-induced mastitis resulted in a time-dependent production of inflammatory cytokines and SAA and Hp in the liver of dairy cows.
Key Words: mastitis • acute phase response • liver biopsy • gene expression
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