Respiratory muscle dysfunction is implicated in the pathophysiology of
obstructive sleep apnea syndrome (OSAS), an oxidative stress disorder prevalent in men.
Pharmacotherapy for OSAS is an attractive option, and
antioxidant treatments may prove beneficial. We examined the effects of chronic intermittent
hypoxia (CIH) on breathing and pharyngeal dilator muscle structure and function in male and female rats. Additionally, we tested the efficacy of
antioxidant treatment in preventing (chronic administration) or reversing (acute administration) CIH-induced effects in male rats. Adult male and female Wistar rats were exposed to alternating cycles of normoxia and
hypoxia (90 s each; Fi(O(2)) = 5% O(2) at nadir; Sa(O(2)) ∼ 80%) or
sham treatment for 8 h/d for 9 days.
Tempol (1 mM,
superoxide dismutase mimetic) was administered to subgroups of
sham- and CIH-treated animals. Breathing was assessed by whole-body plethysmography. Sternohyoid muscle contractile and endurance properties were examined in vitro. Muscle fiber type and cross-sectional area and the activity of key metabolic
enzymes were determined. CIH decreased sternohyoid muscle force in male rats only. This was not attributable to fiber transitions or alterations in oxidative or glycolytic
enzyme activity.
Muscle weakness after CIH was prevented by chronic
Tempol supplementation and was reversed by acute
antioxidant treatment in vitro. CIH increased normoxic ventilation in male rats only. Sex differences exist in the effects of CIH on the respiratory system, which may contribute to the higher prevalence of OSAS in male subjects.
Antioxidant treatment may be beneficial as an adjunct OSAS
therapy.