Effects of an endothelin receptor antagonist and nitroglycerin on digital vascular function in horses during the prodromal stages of carbohydrate overload-induced laminitis.

The research study investigates how an endothelin (ET) receptor antagonist and nitroglycerin affect blood circulation in horses suffering from early stages of laminitis caused by carbohydrate overload (CHO). The study found these treatments significantly improved blood flow and reduced vascular resistance.

Objective and Methodology

• The aim of the study was to scrutinize any alternations in the vascular function of horses induced with carbohydrate overload (over-feeding of concentrates or grains)-induced laminitis, a painful disease in horses affecting their hooves, and the impacts of an endothelin (ET) receptor antagonist and nitroglycerin on the vascular dysfunction associated with laminitis.
• The researchers used 20 adult horses with no existing digit or hoof abnormalities, as the subjects of this study. Each horse received a carbohydrate ration through a nasogastric tube.
• The horses were divided into four groups of five, each group receiving a different treatment (either saline solution or ET receptor antagonist) administered into the digital arterial circulation based on two different schedules.
• The team collected hemodynamic (relating to the flow of blood) variable data before the administration of the CHO rations (referred to as the baseline data) and then collected data every hour after the administration.
• Important parameters such as blood flow and arterial, venous, and capillary pressures were measured along with total, precapillary, and postcapillary resistances in the isolated perfused digit (hoof) of each horse subject.

Results

• The results showcased a significant decrease in right atrial pressure by the 14th hour after the administration of CHO. This decrease wasn’t affected by the administration of either saline solution or ET receptor antagonist, showing these treatments didn’t impact the right atrial pressure.
• CHO also led to a notable decrease in digital blood flow and an increase in total and postcapillary resistances in the isolated digits of anesthetized horses. This suggests that the carbohydrate overload negatively affects the vascular flow in the hooves, which is consistent with laminitis symptoms.
• However, treatment with the ET receptor antagonist and nitroglycerin caused a noticeable decrease in total resistance, while postcapillary resistance significantly decreased with treatment by the ET receptor antagonist but not altered with nitroglycerin treatment.

Conclusion

• Results of the study suggested that treatment with an ET receptor antagonist and nitroglycerin could help in improving vascular resistance in isolated perfused digits of anesthetized horses suffering from CHO-induced laminitis. This could be an important finding in managing laminitis in horses, especially in its early stages.