Plasma and urine nitric oxide concentrations in horses given below a low dose of endotoxin.

The research evaluates the change in plasma and urine nitric oxide concentrations in horses given a low dose of endotoxin, noting how urinary concentrations decrease despite an inflammatory response, while plasma concentrations remain unchanged.

Study Design

• The research involved 11 healthy, adult female horses. Out of these, eight horses were given a low dose of endotoxin (35 ng/kg of body weight) intravenously over a period of 30 minutes.
• Three horses, referred to as the sentinel group, were given an equivalent volume of saline solution instead, acting as a control group.
• Various factors were recorded and monitored in both group of horses, such as signs of disease, hemodynamic variables (those associated with the flow of blood), and nitric oxide (NO) concentration in the plasma and urine.
• These measurements were taken before the endotoxin or saline was given (t=0), and then repeatedly at hourly or bi-hourly intervals up to 24 hours post-infusion.

Results

• In the group treated with endotoxin, there was no apparent change in plasma NO concentrations across the observed time period.
• However, there was a significant decrease in urine NO concentration 4 hours after endotoxin infusion, and again 20-24 hours after infusion.
• Other signs of endotoxemia, an illness resulting from endotoxins in the blood, were present in the treated group. This included observable clinical symptoms and abnormities in hemodynamic, metabolic, and hematologic (blood-related) variables.
• The study also noted increases in serum interleukin-6 and tumor necrosis factor concentrations within hours after endotoxin infusion, indicating the presence of an inflammatory response against endotoxin.

Conclusions

• The findings suggest that horses’ plasma and urine NO concentrations do not increase after infusion of a low dose of endotoxin.
• This is despite the evident induction of an inflammatory response, as signified by increased interleukin-6 and tumor necrosis factor levels, clinical symptoms, and alterations in hemodynamic, metabolic, and hematologic variables.