Lung region and racing affect mechanical properties of equine pulmonary microvasculature.

This research article investigates the impact of racing and lung region on the mechanical characteristics of horse’s pulmonary microvasculature. The study was motivated by the performance-limiting condition in racehorses known as exercise-induced pulmonary hemorrhage, which is related to severe pathologies including small pulmonary vein remodeling.

Research Purpose and Hypothesis

• The primary goal of this research was to examine any regional differences in the mechanical characteristics of the pulmonary arteries and veins of horses, an aspect that had not been studied before.
• The researchers hypothesized that in control animals, there would not be substantial differences in these properties. However, they believed racing and venous remodeling might affect these properties in the caudodorsal (CD) area of the lung.

Methodology

• Pulmonary arteries and veins were harvested from eight control and seven raced horses. The arterial and venous samples were then subjected to wire myography, a technique applied to measure the mechanical properties of blood vessels.
• The researchers also compared length-tension data between vessel type in different lung regions (CD and cranioventral (CV)) and the status of the horse (whether it was a control or raced horse).

Findings

• The study found that pulmonary veins have stiffer walls than pulmonary arteries.
• It also identified that CD pulmonary arteries are generally stiffer than CV arteries, while the opposite was noted in veins – CV veins were found stiffer than CD veins.
• An important revelation of the study was that racing increases the stiffness of CD pulmonary veins and to a lesser extent, CV arteries. For instance, at an internal diameter of 305 μm, the tension in the CD veins and CV arteries of raced horses was significantly higher than in control horses.

Significance

• This research is considered crucial since it is the first report documenting the effect of region and/or exercise on the mechanical properties of small pulmonary vessels in horses.
• The findings of increased stiffness in the veins and arteries of raced horses suggest a possible link between pulmonary vein remodeling and the pathogenesis of exercise-induced pulmonary hemorrhage.