title: Reversible inhibition of human platelet activation by hypothermia in vivo and in vitro.
abstract: A hypothermia-induced hemorrhagic diathesis is associated with cardiopulmonary bypass, major surgery, and multiple trauma, but its pathophysiological basis is not well understood. We examined the hypothesis that hypothermia reversibly inhibits human platelet activation in vitro and in vivo. Platelet activation was studied in normal volunteers by whole blood flow cytometric analysis of modulation of platelet surface GMP-140 and the glycoprotein (GP) Ib-IX complex in: a) shed blood emerging from a standardized in vivo bleeding time wound; b) peripheral blood activated in vitro with either thrombin (in the presence of gly-pro-arg-pro, an inhibitor of fibrin polymerization) or the stable thromboxane (TX) A2 analogue U46619. Platelets in peripheral whole blood were activated at temperatures between 22 degrees C and 37 degrees C. the forearm skin temperature was maintained at temperatures between 22 degrees C and 37 degrees C prior to and during the bleeding time incision. Platelet aggregation was studied in shed blood by flow cytometry and in peripheral blood by aggregometry. Generation of TXB2 (the stable metabolite of TXA2) was determined by radioimmunoassay. In vitro, hypothermia inhibited both thrombin- and U46619-induced upregulation of GMP-140, downregulation of the GPIb-IX complex, platelet aggregation, and TXB2 generation. These inhibitory effects of hypothermia were all completely reversed by rewarming the blood to 37 degrees C. In vivo, platelet activation was inhibited by hypothermia as shown by 5 independent assays of shed blood: upregulation of GMP-140, downregulation of the GPIb-IX complex, platelet aggregate formation, TXB2 generation, and the bleeding time.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pediatrics, University of Massachusetts Medical School, Worcester 01655.
authors.forename: A D
authors.initials: AD
authors.lastname: Michelson
authors.forename: H
authors.initials: H
authors.lastname: MacGregor
authors.forename: M R
authors.initials: MR
authors.lastname: Barnard
authors.forename: A S
authors.initials: AS
authors.lastname: Kestin
authors.forename: M J
authors.initials: MJ
authors.lastname: Rohrer
authors.forename: C R
authors.initials: CR
authors.lastname: Valeri
mesh_terms: D000328:Adult; D000595:Amino Acid Sequence; D001760:Bleeding Time; D015536:Down-Regulation; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D019007:P-Selectin; D015539:Platelet Activation / Q000502:physiology*; D010974:Platelet Aggregation / Q000502:physiology; D010980:Platelet Membrane Glycoproteins / Q000032:analysis / Q000097:blood; D011956:Receptors, Cell Surface / Q000032:analysis; D013929:Thromboxane B2 / Q000096:biosynthesis; D015854:Up-Regulation
chemical_list: D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins; D011956:Receptors, Cell Surface; C028254:von Willebrand factor receptor; D013929:Thromboxane B2