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Circulating big endothelin-1 is disproportionately elevated in obstructive sleep apnea
Plasma endothelin-1 (ET-1) elevations have been associated with cerebrovascular pathology. Previously reported elevations in obstructive sleep apnea (OSA) may indicate cerebral injury, cerebrovasoactive strain of sleep-related breathing disturbances (SRBD), or a secondary peripheral release.
Thus, plasma ET-1 and big ET-1 concentrations were measured in 26 severe untreated and treated OSA patients. Blood samples were taken in the evening, twice during sleep, in the morning, and one hour after awakening.
Despite marked SRBD plasma ET-1 concentrations in OSA were not pathologically elevated, nor changed during baseline sleep or under CPAP-treatment. In contrast, baseline plasma big ET-1 was twofold increased, slightly decreased under long-term CPAP, but still remained within the pathological range.
Marked cerebrovascular challenges resulting from SRBD do not cause any pathological increase of peripherally measurable plasma ET-1. Disproportionate big ET-1 elevations being quite stable even under sufficient treatment suggest an activation of the entire systemic endothelium above underlying breathing disturbances.