Leukotriene B4 levels in the arterial blood of asthmatic patients and the effects of prednisolone.

Prednisolone is very effective in controlling wheezing attacks of bronchial asthma, but its mechanism and the pathogenic role of leukotriene B4 remain unclear. We measured changes in plasma levels of leukotriene B4 in an open study during the clinical course of bronchial asthma, with or without water-soluble prednisolone treatment. Two millilitres of blood was drawn from the radial artery of patients on three occasions: 1) during remission; 2) on admission to hospital with an asthma attack; and 3) 2 days after admission and treatment with intravenous prednisolone (1,000 mg.day-1). Leukotriene B4 was detected by chromatographic fractionation and radioimmunoassay. In 11 asthmatic patients, leukotriene B4 levels on the three occasions were 26.8 (10.7), 106.0 (39.9) and 51.6 (20.2) pg.ml-1 (mean (SD)), respectively. In contrast, the mean leukotriene B4 level of 10 normal controls was 35.9 (10.5) pg.ml-1. Leukotriene B4 levels differed significantly between remission and attack treated without prednisolone, and between attacks treated with and without prednisolone. Mean arterial carbon dioxide (PaCO2) values were 4.8 (0.4) kPa (36.0 (3.0) mmHg), 6.1 (0.4) kPa (45.6 (2.9) mmHg), and 5.5 (0.3) kPa (41.6 (2.0) mmHg), respectively. There were significant differences between these mean PaCO2 values. The mean leukotriene B4 levels on the three occasions were correlated with the mean PaCO2 values. Thus, leukotriene B4 levels in arterial blood reflect the severity of asthmatic attacks and may be affected by intravenous prednisolone.