Mechanism Whereby Platelets Support the Endothelium

Abstract

Thrombocytopenic guinea pigs (platelet count reduced by total body irradiation) were transfused with tritium‐tagged diisopropylfluorophosphonate‐labeled donor platelets. Electron autoradiographs were prepared of tissue taken at various intervals following the transfusion. Some label was found in the endothelial cells three minutes after completion of the transfusion and many platelets were observed interacting with the endothelial membrane. Thirty minutes later much label was found localized only in the endothelial cells with few platelets interacting with the endothelial membrane. The mechanism whereby platelets nourish the endothelial cells by interacting with them is initiated as soon as donor platelets contact deprived endothelium. Transfusion of platelet‐poor plasma containing ten times the amount of label in the platelet concentrates resulted in 87 per cent of the label remaining in the plasma and red blood cells with no localization in the endothelium.