Gas chromatographic-mass spectrometric determination of leukotriene E4 in human urine using deuterium-labelled leukotriene E4 standards.

The utility of two deuterium-labelled leukotriene (LT) E4 analogs, e.g. [20,20,20-2H3]LTE4 and [14,15,17,17,18,18-2H6]LTE4, as internal standards for the determination of LTE4 in human urine by gas chromatography—mass spectrometry (GC—MS) was investigated. 2H-Exchange during hydrogenation occurred both in [20,20,20-2H3]LTE4 and [14,15,17,17,18,18-2H6]LTE4 in an extent of 9.4 ± 0.5% and 67.3 ± 0.6% (mean ± S.D., n = 6), respectively. The lower extent of 2H-exchange in [20,20,20-2H3]LTE4 allowed a more accurate quantitation than the use of [14,15,17,17,18,18-2H6]LTE4. Applying [20,20,20-2H3]LTE4 as internal standard the coefficients of variation for the intra- and inter-assay determination of LTE4 in human urine were 5.7% and 6.2% (n = 4), respectively. The inter-assay coefficient of variation for [14,15,17,17,18,18-2H6]LTE4 was 15%. Using [20,20,20-2H3]LTE4 as internal standard and GC—MS, healthy volunteers were found to excrete 17 ± 10 nmol LTE4 per mol creatinine (mean ± S.D., n = 11). Similar excretion rates for LTE4 in urine of healthy volunteers were found using GC—tandem MS with [1,1-18O2]LTE4 as internal standard. Our results demonstrate that [20,20,20-2H3]LTE4 is a suitable internal standard for the GC—MS determination of urinary LTE4.