A simple and sensitive radioreceptor assay for leukotrienes

A simple and sensitive radioreceptor assay (RRA) for leukotrienes (LTs) was developed using a highly specific [3H]leukotriene D4 (LTD4) binding to guinea pig lung membrane homogenates. The assay can detect down to 0.15 pmol of LTD4. The values for fifty percent inhibition of bound [3H]LTD4 was 1.5 nM for LTD4, 45 nM for LTC4 and 24 nM for LTE4. LTB4 at 3.0 X 10(-5)M had no effect on [3H]LTD4 binding. The RRA for LTs in the absence of serine-borate complex was bi-specific for both LTC4 and LTD4. However, in the presence of 20 mM serine-borate this method was highly specific for LTD4. Recovery rate averaged 87.2% after ethanol extraction and evaporation of known amounts of LTD4. When the radioreceptor assay and radioimmunoassay data for leukotriene levels in the samples were compared to each other, an excellent correlation was observed with a correlation coefficient 'r' of 0.992. The assay was also validated by quantitation of Lts released from human granulocytes stimulated with calcium ionophore, A23187. The method is simpler, less expensive, and more specific for LTD4 than the other methods such as high pressure liquid chromatography and radioimmunoassay and is suitable for routine measurement of either LTD4 specifically or LTC4 plus LTD4 simultaneously in one cell system.