Leukotriene C4 receptors on guinea pig tracheocytes.
Leukotriene (LT) C4 receptors have been characterized on freshly isolated guinea pig tracheal epithelial cells (tracheocytes). The [3H]LTC4 receptor affinity was enhanced by increasing the sodium (60-160 mM) and the magnesium (0-10 mM) concentrations. Low concentrations of calcium (0-3 mM) increased [3H]LTC4 binding, but high concentrations (3-10 mM) decreased it. The pH (6.5-8.0) had no effect on [3H]LTC4 binding to tracheocytes. Under our experimental conditions, binding equilibrium was reached after 20 min. The association and the dissociation rate constants were estimated to be 2.75 +/- 0.25 x 10(6) M-1.min-1 and 0.093 +/- 0.008 min-1, respectively. The Kd (35.4 +/- 8.6 nM) and the Bmax values (2.4 +/- 0.6 x 10(5) receptors/cell) were determined by Scatchard analysis. LTB4, LTD4 and LTE4 did not inhibit [3H]LTC4 binding to the receptors. However, the compound FPL 55712 inhibited the binding of [3H]LTC4 with an IC50 value of 9.0 +/- 1.0 microM. [3H]LTC4 was not metabolized during the binding assays, as confirmed by reverse-phase high-performance liquid chromatography. The lack of [3H]LTC4 binding to glutathione-S-transferase was demonstrated in the presence of an excess of reduced glutathione. LTC4 produced a concentration-dependent increase of free Ca++ in tracheocytes. Our results suggest that guinea pig tracheocytes possess a specific LTC4 receptor coupled to a Ca++ signaling pathway. This LTC4 receptor may play a key role in the epithelium-dependent responses of airway smooth muscle.
Prié
S
S
Department of Pharmacology, Faculty of Medicine, University of Sherbrooke, P.Q. Canada.
Guillemette
G
G
Boulay
G
G
Borgeat
P
P
Sirois
P
P
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004848:Epithelium / Q000648:ultrastructure; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D017997:Leukotriene C4 / Q000378:metabolism / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D018077:Receptors, Leukotriene / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D012680:Sensitivity and Specificity; D012964:Sodium / Q000494:pharmacology; D014132:Trachea / Q000378:metabolism / Q000648:ultrastructure*; D014316:Tritium
D018077:Receptors, Leukotriene; C083173:leukotriene C4 receptor; D014316:Tritium; D017997:Leukotriene C4; D009569:Nitric Oxide; D012964:Sodium; D008274:Magnesium; D002118:Calcium