title: Evaluation of PAF antagonists using human neutrophils in a microtiter plate assay.
abstract: This paper describes a testing model for the detection and evaluation of PAF antagonists, based on the inhibition of PAF-elicited elastase release by human neutrophils. Incubations are performed in microtiter plates in the presence of a specific fluorogenic elastase substrate allowing direct measurement of the exocytosis response by means of a 96-well fluorescence reader. Determinations of the IC50 values for five established PAF antagonists, Ro 19-3704, BN 52021, CV-3988, 48740 RP and kadsurenone, showed that the new model is comparable in sensitivity and discriminative capacity to other in vitro assays. From the effect of antagonists on the PAF concentration-response curve pA2 values could be calculated and information on the type of antagonism obtained. BN 52021 was found to behave as a competitive antagonist while Ro 19-3704 showed a more complex type of inhibition. As a one-plate system, the test is simple to handle and highly reproducible, and appears therefore particularly useful for large drug screening programs.
mesh_terms: D001572:Benzofurans / Q000494:pharmacology; D004224:Diterpenes; D005089:Exocytosis / Q000187:drug effects; D005453:Fluorescence; D046934:Ginkgolides; D006801:Humans; D007783:Lactones; D017705:Lignans; D008722:Methods; D009504:Neutrophils / Q000187:drug effects*; D010196:Pancreatic Elastase / Q000378:metabolism; D010742:Phospholipid Ethers; D010936:Plant Extracts / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D001572:Benzofurans; D004224:Diterpenes; D046934:Ginkgolides; D007783:Lactones; D017705:Lignans; D010742:Phospholipid Ethers; D010936:Plant Extracts; D010972:Platelet Activating Factor; D011725:Pyridines; D013844:Thiazoles; C037913:CV 3988; C052520:3-(3-pyridinyl)-1H,3H-pyrrolo(1,2-c)thiazole-7-carboxamide; C044540:kadsurenone; C045856:ginkgolide B; D010196:Pancreatic Elastase