Specificity and cellular distribution of human polymorphonuclear leucocyte receptors for leukotriene C4.

Human polymorphonuclear (PMN) leucocytes bind synthetic [³H]-labelled leukotriene C4 ([³H]LTC₄), with rapid saturation and reversibility of approximately 90%, by a 700-fold higher concentration of non-radioactive LTC₄. [³H]LTC₄ is recognized specifically by 10,778±6260 (mean ± SD) sites per PMN leucocyte that exhibit a K_D of 34·3 ± 1·7 nM. The specificity of the LTC₄ receptors is supported by the competitive inhibition of binding of [³H]LTC₄ by LTC₄, LTC₄- sulphone, LTD₄, and LTE₄ with relative potencies of approximately 100:20:3:1. The four-fold higher level of specific binding of[³H]LTC₄ by sonicates than by intact PMN leucocytes is attributable to intracellular receptors. Of the total number of receptors recovered in sonicates of PMN leucocytes, one-third are associated with membranes and the other two-thirds with lysosomal granules. The affinity of the membrane receptors for LTC₄ is indistinguishable from that of receptors on intact PMN leucocytes, whereas the affinity of granule receptors is significantly higher. The characteristics of the receptors are consistent with a role in mediating uptake and metabolism of LTC₄ by PMN leucocytes. [ABSTRACT FROM AUTHOR]