Effects of hydrogen peroxide on isolated trachealis muscle of horses.

This study investigates how hydrogen peroxide affects the muscle responses in horse tracheas, particularly during instances when horses experience recurrent airway obstruction, and finds that high concentrations of hydrogen peroxide can influence the responses of airway smooth muscle through neurotransmission, muscarinic receptors, and further downstream, from receptors.

Objective of the Research

• The main aim of the research was to examine how hydrogen peroxide affects the contractile responses of the trachealis muscle, a smooth muscle located in the horse’s windpipe, and how it interacts with other substances in this context. This is pertinent as horses can get accumulation of reactive oxygen species in their airways notably during incidents of recurrent airway obstruction. Hydrogen peroxide is one such reactive oxygen species product.

Methods

• The experiment involved exposing isolated horse trachealis muscle to hydrogen peroxide ranging from 1 microM to 0.1M in concentration.
• Contractile responses of the muscle before and after incubation with hydrogen peroxide was measured. The contractile responses were against a number of stimuli such as acetylcholine, electrical field stimulation (EFS), 127 mM KCl, and relaxation responses to isoproterenol and activation of the nonadrenergic noncholinergic inhibitory response (iNANC).

Findings

• The muscle contractile responses were found to increase in a concentration-dependent manner with hydrogen peroxide, starting from 1 mM.
• The study also found that this contraction of the trachealis muscle did not owe to the release of prostaglandins, acetylcholine or other neurotransmitters, as evidenced by unaffected responses in the presence of atropine, tetrodotoxin, and meclofenamate.
• It was concluded that hydrogen peroxide, at high concentrations, affected the responses of the airway smooth muscle through influences on neurotransmission, muscarinic receptors, and downstream from the receptors. Some of these effects were partially mediated by cyclooxygenase products.
• In the presence of meclofenamate, a non-steroidal anti-inflammatory drug, there was observed a significant partial protection against hydrogen peroxide.
• However, the study found that hydrogen peroxide did not influence the relaxation responses triggered by beta-adrenergic or the nonadrenergic noncholinergic inhibitory response (iNANC).