thromboxane-b2 and Sleep-Apnea-Syndromes

Since obstructive sleep apnea syndrome (OSAS) is often linked with systemic hypertension, we sought to clarify the characteristics of prostanoid metabolism in OSAS. In 7 OSAS patients (apnea-hypopnea index, 51.0 +/- 23.4) and 7 non-snorers as control, nocturnal urine was sampled and analyzed for stable metabolites of prostacyclin (PGI2) and thromboxane A2 (TxA2), [6-keto-PGF1alpha and thromboxane B2 (TxB2)]. The ratio of 6-keto-PGF1alpha to TxB2 was significantly higher in OSAS (2.97 +/- 1.52) than in control (1.38 +/- 0.38). Successful treatment with nasal continuous positive airway pressure (8.3 +/- 1.5 cmH2O) for 3 days caused a significant decrease in mean blood pressure in OSAS. Moreover, the 6-keto-PGF1alpha to TxB2 ratio also significantly decreased to 1.74 +/- 0.58, a level which may not significantly different from control. These results suggest that the production ratio of PGI2 to TxA2 is shifted toward vasodilatation in untreated OSAS. We conclude that the production of prostanoids plays a role in compensating for the systemic hypertension in OSAS.

Topics: 6-Ketoprostaglandin F1 alpha; Adult; Blood Pressure; Case-Control Studies; Humans; Hypertension; Male; Middle Aged; Oxygen; Positive-Pressure Respiration; Sleep Apnea Syndromes; Thromboxane B2

1. Given the unexplained frequent association between systemic hypertension and obstructive sleep apnoea (OSA), the secretion of prostanoids during sleep was investigated (more specifically, the ratio of prostacyclin (PGI2) to thromboxane A2 (TxA2), since they have marked opposite effects on vascular tone). Prostacyclin has vasodilating effects, whereas thromboxane results in vasoconstriction. 2. In 11 OSA drug-free male patients (age 53 +/- 2 years, mean +/- s.e.m.; apnoea index 55 +/- 15 apnoeas/hour of sleep; body mass index 31 +/- 2 kg/m2), we measured the urinary excretion during sleep of 6-keto-PGF1-alpha and of thromboxane TxB2 (the stable metabolites of prostacyclin PGI2 and of thromboxane A2 respectively). This was done on two consecutive nights; one untreated, the other with nasal continuous positive airway pressure (CPAP) treatment. The results were compared with those of nine normal unobese male subjects. 3. The urinary ratio of 6-keto-PGF1-alpha to TxB2 was significantly (P less than 0.001) lower in the untreated OSA patients (1.7 +/- 0.2) than in the controls (3.1 +/- 0.3). It significantly increased with CPAP treatment to 2.3 +/- 0.2, P less than 0.02, which was no longer different from the controls. 4. These results suggest that OSA is associated with an abnormal release of prostanoids during sleep resulting in a decrease of the prostacyclin to thromboxane ratio which potentially has a vasoconstricting effect. The relationship between these changes and the systemic hypertension often observed in OSA patients remains to be established.

Topics: 6-Ketoprostaglandin F1 alpha; Adult; Epoprostenol; Humans; Hypertension; Male; Middle Aged; Sleep; Sleep Apnea Syndromes; Thromboxane A2; Thromboxane B2