[en] The effect of the specific PAF-antagonist WEB 2086, a thieno-triazolo-diazepine, and ketoprofen, a NSAID, was investigated on PAF-induced bovine platelet aggregation measured ex vivo in platelet-rich plasma (PRP). WEB 2086 was infused intravenously over 1 min followed immediately by ketoprofen administration over 1 s (both drugs = 3 mg/kg), in a group of six healthy male Friesian calves. Depending on the PAF concentration, a reversible (10(-8)-10(-9) mol/l) and irreversible (10(-5)-10(-7) mol/l) platelet aggregation was observed. The reversible aggregation was completely blocked by pretreatment of the animal with WEB 2086 and ketoprofen. The inhibitory effects observed during the irreversible aggregation were 47.22%, 54.00% and 88.00% at 10(-5), 10(-6) and 10(-7) mol/l PAF, respectively. Moreover, the aggregation obtained in these condition became reversible. Maximal inhibitory effect of WEB 2086 and ketoprofen on PAF-induced platelet aggregation in calves was observed within 30 min after administration of both drugs. This inhibition persisted even after 24 h and was significantly different from control with P < 0.05. The combined effect of both drugs exceeded the sum of the individual effects (synergism). It was concluded that WEB 2086 and ketoprofen very effectively blocked PAF-induced bovine platelet aggregation in platelet-rich plasma. The study also suggested a synergism between both substances.
Bastos is recipient of a grant from CNPq and FCAP Belém-Parà Brazil