High-affinity binding site for leukotriene C4 in human erythrocytes.

A specific, high-affinity binding site for leukotriene C4 was identified in human erythrocyte particulate fraction and in vesicle preparation. The binding was saturable, reversible and specific. Vesicle preparations showed that binding sites were localized on the outside of the plasma membrane. The dissociation constant and site density were found to be Kd = 15.9 +/- 3.2 nmol X 1(-1) and N = 152 +/- 35 sites per cell, respectively, as calculated from Scatchard analysis. The effect of leukotriene C4 did not modify the calcium influx and did not inhibit the ATPase-dependent calcium efflux. In this paper, the physiological significance of these sites is discussed.

Specific binding of leukotriene C4 to endothelial cell membranes.

Vascular endothelium is a target for leukotriene C4 (LTC4) as demonstrated by previous in vivo and culture experiments. Binding assays were carried out at 0 degrees C on membrane fraction obtained from bovine aortic endothelial cells in culture. Specific binding sites (Kd = 49.9 +/- 6.3 nmol X 1(-1), N = 1.2 X 10(6) sites per cell) for LTC4 were demonstrated in this preparation. Competition studies showed that LTB4, LTD4 and LTE4 did not displace LTC4 from its binding sites. FPL 55712, a sulfidopeptide antagonist, was seen to be a weak competitor and reduced glutathione exhibited a significant affinity for the binding site. The possible receptor role of this site is discussed.