Analysis of leukotriene B4 in human lung lavage by HPLC and mass spectrometry

Although leukotrienes are beleived to mediate symptoms of human lung disease, there is little direct evidence of their existence in the lung. This is due to the difficulty in obtaining lung samples, the small amounts of leukotrienes typically present in such samples and the problems associated with purifying and analyzing leukotrienes in complex biological samples. In this study, lung lavagates were collected and analyzed for leukotrienes. The methods in this analysis included solid phase extraction using a C-18 reverse phase cartridge followed by HPLC using a new photodiode array detector which provides full UV spectra of eluting compounds. Lung lavage fluid from a patient with chronic pulmonary disease contained a compound with a UV spectra of LTB₄ which was found to elute with synthetic ³H]-LTB₄. This compound was confirmed as PTB using gas chromarography/mass spectrometry in the negative ion-chemical ionization mode. The inclusion of oxygen-18 LTB₄ as an internal standard allowed approximate quantitation of the amount of LTB₄ present in this 5 ml lung lavagate as 40–50 ng.