Endothelin-1 plasma levels are not elevated in patients with obstructive sleep apnoea

Endothelin-1 (ET-1), a potent vasoconstrictor, is released mainly by vascul ar endothelial cells under the influence of hypoxia and other stimuli. ET-1 is related to endothelial dysfunction, as well as arterial and pulmonary h ypertension, all of which are thought to be associated with obstructive sle ep apnoea (OSA). This study evaluated venous plasma concentrations of ET-1 and noradrenaline and 24-h systemic blood pressure in 29 patients with OSA (age=56.9+/-1.6 y rs; body mass index=29.5+/-0.7 kg.m(-2) (mean+/-SEM)). Blood samples were t aken in the morning, evening and during sleep. In the same way, the patient s mere assessed during a night of continuous positive airway pressure (CPAP ) and after 13.9+/-1.4 months while still on CPAP. ET-1 levels were compare d to those of control subjects, who were selected from in- and outpatients and were matched to patients for age, sex, presence of arterial hypertensio n and coronary artery disease. ET-1 plasma levels were not elevated in the patients compared to the contro ls (41.6+/-2.2 and 44.9+/-1.3 pg.mL(-1), respectively, p=0.20). The ET-1 co ncentration did not change significantly, neither during sleep nor in the f irst night on CPAP therapy, nor under long-term treatment with CPAP. ET-1 n either correlated to the severity of OSA nor to that elf systemic hypertens ion. The results suggest that endothelin-l does not play a crucial role in the p athophysiology of obstructive sleep apnoea.