CHARACTERIZATION OF LEUKOTRIENE RECEPTORS ON RAT LUNG STRIP

The leukotriene receptor(s) present on rat lung strip have been charac terised using the natural agonists, a selective mimetic, and potent (c ysLT(1)) selective leukotriene receptor antagonists. Leukotriene C-4 a nd leukotriene D-4 displayed comparable contractile potencies whilst l eukotriene E(4) was less potent. However, both leukotriene D-4 and leu kotriene E(4) were found to be partial agonists relative to leukotrien e C-4. Responses to all three leukotrienes were competitively antagoni sed by ICI 198615 2-methoxy-(4-phenylsulfonyl)-aminocarbonyl)-phenyl m ethyl)-1H-indazol-6-yl) carbonic acid cyclopentyl eater), SK&F 104353 (2-(R)-hydroxy-3(S)-(2-carboxyethylthio) acid, and MK571 -3-[3-[2-(7-c hloro-2-quinolin-yl)ethenyl]-phenyl)- lamino)3-oxopropyl]thio]methyl]t hio]thio]propanoic acid) with comparable affinities irrespective of th e agonist used. This indicates that rat lung contains a homogeneous po pulation of leukotriene receptors and that they are of the CysLT(1) ty pe.