In vitro investigation of the effects of cyclooxygenase-2 inhibitors on contractile activity of the equine dorsal and ventral colon.

The researchers investigated how two types of drugs, which inhibit cyclooxygenase (COX)-2, affect the muscle activity in the upper and lower parts of horse colons. They found that the effect varies with the type of drug, with etodolac having the least impact.

Study Design

• The study considered the effects of two cyclooxygenase (COX)-2 inhibitors on the contractile activity of the circular smooth muscle layer present in the horses’ dorsal (upper) and ventral (lower) colon.
• The COX-2 inhibitors under focus were nonsteroidal anti-inflammatory drugs (NSAIDs), specifically etodolac, nabumetone, and indomethacin.
• To obtain viable samples, full-thickness tissue samples from the dorsal and ventral colon of 10 healthy horses were acquired. The specimens were obtained from specialized regions: the diaphragmatic flexure in the dorsal colon, and the sternal flexure from the ventral colon.

Methodology

• The obtained samples were cut into strips, following the fiber alignment of the circular muscle layer.
• These muscle samples were then submerged within a tissue bath system, the environment where contractile strength measurements were conducted.
• Incremental amounts of the three NSAIDs – etodolac, nabumetone, and indomethacin – were gradually introduced, and the changes in muscle contraction were monitored and recorded.

Results

• The research found varying responses in the dorsal and ventral colon of the horses to the administered NSAIDs.
• Specifically, indomethacin led to the biggest reduction in contraction activity, followed closely by nabumetone.
• Among the three, etodolac was observed to have the minimal impact on contractile activity. The difference from the initial (baseline) values in muscle contraction for etodolac was only significant at the highest concentration used in the ventral colon area.

Conclusions

• The variation in impact on muscle contraction by the COX-2 targeted NSAIDs may have different implications for equine health. Specifically, these effects are significant in how these drugs impact the motility of the digestive tract in horses.
• Given that etodolac had the smallest impact on the contractile activity, the research suggests that it might indeed have fewer adverse effects relating to the motility of the dorsal and ventral colon in comparison with nabumetone and indomethacin.