Leukotriene C4 receptors on guinea pig tracheocytes
Prié, S.; Guillemette, G.; Boulay, G.; Borgeat, P.; Sirois, P.
Journal of Pharmacology and Experimental Therapeutics 275(1): 312-318
1995
ISSN/ISBN: 0022-3565 PMID: 7562565 Document Number: 451778
Leukotriene (LT) C-4 receptors have been characterized on freshly isolated guinea pig tracheal epithelial cells (tracheocytes). The (3H)LTC-4 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)LTC-4 binding, but high concentrations (3-10 mM) decreased it. The pH (6.5-8.0) had no effect on (3H)LTC-4 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 times 10-6 M-1 cntdot min-1 and 0.093 +- 0.008 min-1, respectively. The K-d (35.4 +- 8.6 nM) and the B-max values (2.4 +- 0.6 times 10-5 receptors/cell) were determined by Scatchard analysis. LTB-4, LTD-4 and LTE-4 did not inhibit (3H)LTC-4 binding to the receptors. However, the compound FPL 55712 inhibited the binding of (3H)LTC-4 with an IC-50 value of 9.0 +- 1.0 mu-M. (3H)LTC-4 was not metabolized during the binding assays, as confirmed by reverse-phase high-performance liquid chromatography. The lack of (3H)LTC-4 binding to glutathione-S-transferase was demonstrated in the presence of an excess of reduced glutathione. LTC-4 produced a concentration-dependent increase of free Ca++ in tracheocytes. Our results suggest that guinea pig tracheocytes possess a specific LTC-4 receptor coupled to a Ca++ signaling pathway. This LTC-4 receptor may play a key role in the epithelium-dependent responses of airway smooth muscle.