Inhibition of PAF-induced systemic responses in the rat, guinea pig, dog and primate by the receptor antagonist SRI 63-441.
Systemic administration of synthetic PAF produces a number of dose-dependent circulatory effects in a variety of species. We have evaluated a novel PAF antagonist, SRI 63-441, for its ability to inhibit PAF-induced effects in the rat, guinea pig, dog and primate. In the rat, a 100 ng kg-1 i.v. PAF challenge produced a (mean +/- 1 S.D.) 39 +/- 5% decrease in carotid blood pressure. Prior injection of SRI 63-441 inhibited this hypotensive response in a dose-dependent manner, with an ED50 of 0.15 mg kg-1 i.v. In the guinea pig, PAF at 100 ng kg-1 elicited a 50 +/- 8% increase in hematocrit and a 50 +/- 11% elevation in bronchial resistance. The ED50 values for inhibition by SRI 63-441 of these two physiological parameters were 0.012 mg kg-1 and 0.035 mg kg-1 i.a., respectively. Dogs challenged with 1.5 micrograms kg-1 PAF i.v. exhibited 28.7 +/- 6.5% increase in hematocrit 10 min after injection. The ED50 value for SRI 63-441 inhibition of hemoconcentration in the dog was 0.18 mg kg-1 i.v. In the primate model of PAF-induced hemoconcentration, controls responded to 3.5 micrograms kg-1 i.v. PAF with a 30 +/- 6% increase in hematocrit. Using the primates in a cross-over design, the ED50 of SRI 63-441 was 0.11 mg kg-1 i.v. At this ED50 value, the ratio of nmol kg-1 PAF used versus nmol kg-1 antagonist is approximately 1:25. The effectiveness of SRI 63-441 in these models suggest potential clinical applications in disease states involving hyperpermeability and pulmonary dysfunction.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002428:Cebus; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006400:Hematocrit; D006439:Hemodynamics / Q000187:drug effects*; D007022:Hypotension / Q000503:physiopathology; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000502:physiology; D008297:Male; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors*; D011806:Quinolinium Compounds / Q000494:pharmacology*; D051381:Rats; D013045:Species Specificity
D010972:Platelet Activating Factor; D011806:Quinolinium Compounds; C050531:SRI 63-441