The effect of prophylactic anti-asthma drugs on PAF-induced platelet accumulation in the thorax of the guinea pig.

Intravenous infusion of platelet activating factor (PAF) causes an accumulation of platelets within the thorax of the guinea pig that is accompanied by increased sensitivity of the airways to spasmogens. A crystal scintillation detector has been used for measurement of intrathoracic accumulation of 111Indium-labeled platelets during responses to PAF. PAF-antagonists inhibit development of airway hyperreactivity, do not diminish platelet accumulation in response to an intravenous infusion of PAF. It is therefore concluded that intrathoracic platelet accumulation per se is not the determinant of increased airway reactivity.