Interation 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 conferment of protection against subsequent γ-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°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 Na²⁺ were not required for binding, and binding was not altered by GTP, ATP, or cAMP, by leikotrienes C₄, D₄, or E₄, or by the leokotriene 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 × 10⁵ sites/cell] and low-affinity [Kd = 350 ± 211 nM, approximately 2.7 × 10⁶ 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.