Changes in platelet β‐thromboglobulin, fibrinogen, albumin, 5‐hydroxytryptamine, ATP, and ADP during and after surgery with extracorporeal circulation in man

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Abstract
Surgery with extracorporeal circulation (ECC) is associated with transient alterations of platelet function whose pathogenic mechanisms are not completely understood. To define further the platelet abnormalities, we determined the changes in platelet content of several granule-associated substances during and after ECC in patients subjected to aortocoronary bypass surgery. Platelet β-thromboglobulin (β-TG) decreased to 79.8% of the preoperative level at the end of ECC (p < 0.01) and, as expected, did not recover 1 hr after the end of surgery. Platelet fibrinogen and albumin decreased to 67.9% (p < 0.01) and to 29.8% (p < 0.01) of baseline, respectively. However, 1 hr after surgery, platelet fibrinogen rose to 92% and albumin to 55.5% of baseline, denoting that during the recovery from ECC, platelets incorporate some plasma proteins. During ECC, platelet 5-hydroxytryptamine (5-HT) and total ATP and ADP decreased to 50.8% (p < 0.01), 63.2% (p < 0.01), and 69.9% (p < 0.01) of their respective preoperative values, indicating dense body release. One hour after surgery, ATP recovered to 83.8%, suggesting that previous depletion compromised also the metabolic pool of adenine nucleotides. In summary, 1) Our results confirm and extend previous observations demonstrating α-granule release during ECC. 2) Platelets undergoing ECC can incorporate plasma proteins as evidenced by the rapid increase of platelet fibrinogen and albumin after bypass. Although the mechanisms of this increase and site of storage of the exogenous substances are unknown, this observation justifies further studies to determine if internalization of plasma proteins, especially fibrinogen, may take place in physiological conditions. 3) Dense body depletion with transient storage pool deficiency appears to be a component of the reduced platelet function during ECC. 4) Consumption of metabolic ATP with alteration of platelet energy metabolism may further impair platelet function, contributing to the bleeding episodes observed during surgery with ECC.