BLOOD AND BRONCHOALVEOLAR LAVAGE ENDOTHELIN-1 LEVELS IN NOCTURNAL ASTHMA

Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor that was re cently shown to exhibit bronchoconstrictive properties in vitro. In as thmatic patients, the expression of ET-1 peptide was also shown to be increased in endobronchial biopsies. Thus, we postulated that ET-1 cou ld be higher in subjects with nocturnal asthma. Bronchoalveolar lavage (BAL) fluid levels of ET-1 were measured in 10 subjects with nocturna l asthma and 6 normal volunteers at 0400 h (nighttime groups) and in a n additional 7 subjects with nocturnal asthma and 6 control subjects a t 1600 h (daytime groups). ET-1 levels were significantly lower in the nighttime asthmatic group (median 39.3 pg/mg protein, 7.3 to 44.0 IQ) than in the nighttime control group (median 77.4 pg/mg protein, 46.8 to 121.9 IQ; p = 0.01) or the daytime asthmatic group (median 56.8 pg/ mg protein, 51.6 to 97.4 IQ; p = 0.04). ET-1 levels did not differ sig nificantly between the daytime asthmatic and the daytime control group s or between control groups. Additionally, the overnight reduction in lung function was significantly correlated with lower BAL ET-1 levels (r = 0.57, p = 0.05). These results suggest that ET-1 plays a role in the overnight worsening of asthma and perhaps is more tightly tissue b ound, resulting in lower levels of BAL fluid.