Characterization of a leukotriene D4 receptor in guinea pig lung.

Abstract

[3H]Leukotriene D4 was found to bind, in a saturable manner and with exceedingly high affinity, to a membrane preparation from guinea pig lung. Measurement of saturation at equilibrium yielded Kd values of 5.46 ± 0.31 X 10-11 M at 200C and 2.12 ± 0.37 x 10-10 M at 00C while the numbers of binding sites (Bm.) were 384 ± 34 and 302 ± 44 fmol/mg of protein at 20 and at 0C, respectively. The time courses of both association and dissociation were slow but the rate of dissociation was accel-2+ erated by either NaCl or GTP. Binding was enhanced by Ca , Mg2e, and Mn2" and inhibited by Na' but not by LiW or K+, suggesting that the binding of leukotriene D4 may be regulated by ions. Leukotriene E4, but not leukotriene C4, had a high affinity for the putative receptor, consistent with the pharmacological evidence that the actions of leukotrienes D4 and E4 are mediated by a receptor distinct from that for leukotriene C4. Affinities of stereoisomers and related compounds for the leukotriene D4 binding sites closely paralleled their contractile activities in guinea pig lung parenchymal strips. In addition, the antagonist of slow-reacting substance of anaphylaxis, FPL 55712, inhibited the binding of [3H]leukotriene D4 with a K; value of 1 x 10-7 M, which is in agreement with reported Kb values obtained in pharmacological studies.

Neutral endopeptidase-like enzyme controls the contractile activity of substance P in guinea pig lung.

“…Guinea pig lung membranes were prepared essentially according to procedures described previously (30). Lungs from three guinea pigs were perfused with Tyrode's buffer and homogenized by polytron (Brinkmann Instruments Inc.?…”

Inhibition of Radiolabeled Leukotriene-Binding by AS-35 in Guinea Pig Lung Membrane Fraction.

“…The membrane fraction was prepared according to the method of Pong and Dehaven (2). Briefly, male Hartley strain guinea pigs weighing 300 to 500 g were sacrificed, and the lungs were removed and minced into small segments.…”

“…Binding assays were performed according to the method of Pong and Dehaven (2) and competitor drugs at various concentra tions. At the end of incubation, bound radioactivity was separated from free by vacuum filtration through Whatman GF/C fil ters.…”

Involvement of 5-Lipoxygenase Pathway in Norepinephrine Stimulation of Rat Pineal Melatonin Synthesis

“…Re cent observations suggest that both inhibitors are potent an tagonists of leukotriene (mainly leukotriene D4) activity [II,15]. However at the doses employed (1 O'5 M) the drugs may have effects attributable to mechanisms other than leukotriene antagonism, e.g., inhibition of 5-HETE produc tion [8].…”