The association of adrenaline and noradrenaline with blood platelets

Abstract

The distribution of epinephrine and norepinephrine between plasma and blood platelets has been studied by a fluorimetric method. In 116 samples of human plasma the platelets contained, on the average, a little over 50% of the total catecholamines present in platelet-rich plasma. The platelet-bound proportion of epinephrine correlated with the platelet-bound proportion of norepinephrine. The mean amounts contained in 109 platelets were 2 [mu]mg of epinephrine and 7[mu]mg of norepinephrine. ] t was calculated that the concentration of catecholamines is about 125 times higher in platelets than in plasma. The distribution of catecholamines between platelets and plasma was unaffected by contact with uncoated glass surfaces. Some anticoagulants decreased the yield of platelets in platelet-rich plasma by causing clumping and adhesion. Highest platelet yields were obtained with ethylenediaminetetraacetate. No catecholamines passed into serum from platelets during clotting, whether spontaneous or induced. Lysis of platelets by freezing and thawing or by treatment with a surface-active agent resulted in a partial release. Extraction with butanol was practically quantitative. Ethylenediaminetetraacetate increased the disappearance in O2 of platelet-bound catecholamines in vitro. No uptake of epinephrine by platelets was observed in heparinized platelet-rich plasma at an epinephrine concentration of about 10 ug/l. An uptake resulting in a final concentration of platelet-bound epinephrine of about 3 times the initial concentration was found in citrated platelet-rich plasma at an epinephrine concentration of 80-200 fig/1. In confirmation of earlier results an increase of epinephrine was found in platelet-rich plasma after convulsion treatment. This increase was confined to the "free" fraction.