Plasma and urine nitric oxide concentrations in horses given below a low dose of endotoxin.
OBJECTIVE
To quantify plasma and urine nitric oxide (NO) concentrations before and after low-dose endotoxin infusion in horses.


METHODS
11 healthy adult female horses. Procedure-Eight horses were given endotoxin (35 ng/kg of body weight,i.v.) over 30 minutes. Three sentinel horses received an equivalent volume of saline (0.9% NaCl) solution over the same time. Clinical signs of disease and hemodynamic variables were recorded, and urine and plasma samples were obtained to measure NO concentrations prior to endotoxin infusion (t = 0) and every hour until postinfusion hour (PIH) 6, then every 2 hours until PIH 24. Blood for hematologic and metabolic analyses and for serum cytokine bioassays were collected at 0 hour, every hour until PIH 6, every 2 hours through PIH 12, and finally, every 6 hours until PIH 24.


RESULTS
Differences in plasma NO concentrations across time were not apparent, but urine NO concentrations significantly decreased at 4 and 20 to 24 hours in endotoxin-treated horses. Also in endotoxin-treated horses, alterations in clinical signs of disease, and hemodynamic, metabolic, and hematologic variables were significant and characteristic of endotoxemia. Serum interleukin-6 (IL-6) activity and tumor necrosis factor (TNF) concentrations were increased above baseline values from 1 to 8 hours and 1 to 2 hours, respectively.


CONCLUSIONS
Plasma and urine NO concentrations did not increase in horses after administration of a low dose of endotoxin, despite induction of an inflammatory response, which was confirmed by increased TNF and IL-6 values characteristic alterations in clinical signs of disease, and hematologic, hemodynamic and metabolic variables.
Bueno
A C
AC
Department of Veterinary Clinical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803, USA.
Seahorn
T L
TL
Cornick-Seahorn
J
J
Horohov
D W
DW
Moore
R M
RM
D000818:Animals; D001784:Blood Gas Analysis / Q000662:veterinary; D001794:Blood Pressure; D016207:Cytokines / Q000097:blood; D019446:Endotoxemia / Q000276:immunology / Q000378:metabolism / Q000662:veterinary*; D004731:Endotoxins / Q000008:administration & dosage / Q000276:immunology / Q000633:toxicity*; D004927:Escherichia coli Infections / Q000276:immunology / Q000378:metabolism / Q000662:veterinary*; D005260:Female; D005340:Fibrinogen / Q000032:analysis; D005562:Formazans / Q000737:chemistry; D006339:Heart Rate; D006734:Horse Diseases / Q000276:immunology / Q000378:metabolism*; D006736:Horses; D007375:Interleukin-1 / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008163:Luminescent Measurements; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000097:blood / Q000652:urine; D013778:Tetrazolium Salts / Q000737:chemistry; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
D016207:Cytokines; D004731:Endotoxins; D005562:Formazans; D007375:Interleukin-1; D015850:Interleukin-6; D013778:Tetrazolium Salts; D014409:Tumor Necrosis Factor-alpha; C079782:MTT formazan; D009569:Nitric Oxide; C044101:endotoxin, Escherichia coli; D005340:Fibrinogen