抄録
Resting platelets can be induced by epinephrine to shift to an activated state and to form aggregates, a basic event in haemostasis and thrombosis. Interaction of 14C-epinephrine with isolated membranes from human platelets was found to occur via a rapid, specific and reversible reaction which was maximal at 37°C over 60 min with a binding constant of 4.5-5.2 × 107 M-1 and 4-5 × 104 sites per platelet. Membranes become less sensitive to binding of epinephrine following their treatment with-SH group blockers, proteolytic enzymes, beta galactosidase and galactose oxidase. Binding was inhibited to varying degrees by alpha adrenergic agents and by mersalyl, a specific inhibitor of platelet ATPase activity of thrombosthenin, and to a much lesser extent by beta adrenergic agents at higher concentration. Detergent solubilized 14C-epinephrine labelled membranes electrophoresed on acryl-amide gels presented a pattern of labeling with two prominent peaks of radioac-tivity, suggesting that the label entered two components of apparent M.W. >200, 000 and 160, 000 daltons. These results indicate that high molecular weight components located on or within the platelet membrane recognize and bind epinephrine. One suggestion is that the complex phenomenon of platelet activation by epinephrine is initiated by events on the membrane involving an alpha adrenergic type effect of epinephrine binding by platelet membrane.
