Circadian characteristics of urinary leukotriene E4 in healthy subjects and nocturnal asthmatic patients

Study objectives: Circadian rhythmicity of cysteinyl leukotrienes (LTs) and thromboxane (TX)-A(2) in healthy subjects and nocturnal asthmatic patients remains a subject of controversy. The aim of this study was to investigate the contribution of these mediators to the pathogenesis of nocturnal asthma. Methods: We measured peak expiratory flow rate, urinary concentration of LTE4, 11-dehydro-TXB2, and creatinine eight times every 3 h in three groups: healthy control subjects (n = 5, group A), noeturnal asthmatic patients (n = 9, group B), and nonnoeturnal asthmatic subjects (n = 9, group C). To evaluate the reproducibility of the measurement of urinary LTE, we measured urinary LTE in group A for 3 separate days. Results: The urinary LTE4 concentrations froth 3 to 6 AM were significantly (p < 0.05) higher than froth 3 to 6 PM in both group A and group B, but not in group C. The mean levels of LTE4 in group B and group C were significantly higher (p < 0.05) than those in group A. In group B, another small peak was observed from 6 to 9 Pn. No significant day-to-day variation was observed in group A. Urinary 11-dehydro-TXB2 values from 3 to 6 AM were significantly (p < 0.001) higher than those levels From 3 to 6 PM in all groups, and the mean levels in group B and group C were significantly higher than those in group A (p < 0.05). Conclusions: Circadian rhythmicity of urinary LTE4 with a morning peak was found in healthy control subjects and nocturnal asthmatic subjects, but not in nonnocturnal asthmatic patients. It yeas suggested that cysteinyl LTs rather than TXA(2) might contribute to the nocturnal worsening of asthma.