Analysis of the leukotriene D₄ receptor in the granulation tissue of allergic inflammation in rats

Leukotriene (LT) D₄ receptor in the granulation tissue formed in the air pouch-type allergic inflammation model in rats was analyzed. Membrane preparation of the granulation tissue obtained 3-9 days after the antigen challenge has specific binding sites of [³H]LTD₄. Scatchard analysis showed that the affinity (K_d) and the density (B_max) were not changed among the granulation tissue obtained 3-9 days after the antigen challenge. The K_d value in the granulation tissue (0.90 ± 0.12 nM) was close to that in the rat lung (1.00 ± 0.24 nM) and the guinea pig lung (0.86 nM). On the other hand, B_max (62 ±8 fmol/mg protein) in the granulation tissue was higher than that in the rat lung (21 ±4 fmol/mg protein) but was far less than that in the guinea pig lung (405 fmol/mg protein). LTC₄ and LTE₄ inhibited the binding of [³H]LTD₄ to the membrane preparation of the granulation tissue in a concentration-dependent manner. IC50 of LTQ and LTE₄were 1 × 10^-7and 2 × 10^-7 M, respectively. A guanine nucleotide, guanyl-5′-yl-imido-diphosphate (GppNHp), reduced [³H]LTD₄ binding to the membrane preparation of the granulation tissue suggesting that LTD₄ receptors in the granulation tissue are associated with G proteins. These results indicate that LTD₄ binding sites in the granulation tissue arc high affinity receptors for LTD₄. A possible role of LTD₄ in the recurrence of allergic inflammation in the chronic phase is discussed.