IN-VIVO RESPONSES OF MOUSE-BLOOD CELLS TO PLATELET-ACTIVATING-FACTOR (PAF) - ROLE OF THE MEDIATORS OF ANAPHYLAXIS

Intravenous injection of platelet-activating factor (PAF) (0.36 mu mol /kg b.w.) in mice induced severe hemoconcentration, leucopenia, thromb ocytopenia and finally the death of 85% of the tested animals. Combine d inhibition of histamine and serotonin by promethazine and chlorproma zine, 6.24 and 3.12 mg/kg b.w. subcutaneously, protected the mice from PAF in part, reducing the death rate to 43%. These drugs did not prot ect the mice against the PAF-induced hemoconcentration, leucopenia and thrombocytopenia. Sulfinpyrazone (100 mg/kg b.w.) intravenously was t he most effective both in protecting mice from PAF-induced death, redu cing the death rate to 17%, and from thrombocytopenia, although hemoco ncentration persisted. These results indicated that an important compo nent of the PAF-induced systemic effects is mediated by reactions whic h can be inhibited by sulfinpyrazone. Furthermore, PAF-induced thrombo cytopenia is not a direct PAF effect since it can be inhibited by sulf inpyrazone.