Interaction of leukotriene C4 and Chinese hamster lung fibroblasts (V79A03 cells). 1. Characterization of binding

A novel, specific, and potent biological action of leukotriene C4 (LTC4) was demonstrated in the Chinese hamster lung fibroblast cell line V79A03 (V79 cells), namely the confirment of protection against subsequent gamma-irradiation. Consequently, studies were conducted to determine whether LTC4-conferred radioprotection could be attributed to a receptor-mediated phenomenon. Specific binding sites for leukotriene C4 (LTC4) were identified and characterized using intact V79 cells incubated at 4 degrees C in the presence of serine-borate, during which time conversion of LTC4 to LTD4 or LTE4 was undetectable. Binding was maximal in a broad region between pH 6.2 and 8.8. Ca2+, Mg2+, and Na+ were not required for binding, and binding was not altered by GTP, ATP, or cAMP, by leukotrienes B4, D4, or E4, or by the leukotriene end point antagonists LY 171883, FPL 55712, or Revlon 5901-5. Scatchard analyses and kinetic experiments indicated the presence of high-affinity Kd = 2.5 +/- 0.63 nM, approximately 9.9 x 10(5) sites/cell] and low-affinity Kd = 350 +/- 211 nM, approximately 2.7 x 10(6) sites/cell] binding sites. The observed binding characteristics of LTC4 to V79 cells are consistent with a receptor-mediated phenomenon. In a companion communication which follows this report, we report the subcellular distribution of LTC4 binding to V79 cells and demonstrate that this binding is unlikely to be attributed principally to interaction with glutathione-S-transferase.