title: Lactadherin functions as a probe for phosphatidylserine exposure and as an anticoagulant in the study of stored platelets.
abstract: OBJECTIVE
  Annexin V, the long established standard method of measuring phosphatidylserine (PS) exposure, is not the most suitable probe for the study of stored platelets because of calcium dependence and low sensitivity under 8% PS exposure. The aim of this study was to show lactadherin as a sensitive probe for PS exposure and an effective anticoagulant for stored platelets.
  
  
  METHODS
  PS exposure and the associated procoagulant activity of platelets in 20 platelet concentrate units were investigated by flow cytometry, confocal microscopy, coagulation time analysis and enzymatic assays. Annexin V and lactadherin were utilized separately in this study.
  
  
  RESULTS
  Using lactadherin, we identified higher levels of PS exposure on the platelets and microparticles compared to detection using annexin V by flow cytometry. Lactadherin staining showed earlier PS exposure localized to platelets membrane in the earlier stage of storage. Subsequently, PS was distributed on the narrow rim of the plasma membrane and blebbing vesicles. Lactadherin or annexin V(32 nm) prolonged coagulation time 2·4 fold versus twofold. The production of thrombin and intrinsic/extrinsic factor Xase were inhibited approximately 85∼90% and 65∼70% by lactadherin and annexin V, respectively.
  
  
  CONCLUSIONS
  Lactadherin can provide the quantification and location of PS exposure on banked platelets in the absence of agonists. Furthermore, lactadherin is a more effective anticoagulant for inhibiting the procoagulant activity of stored platelets compared with annexin V.
authors.affiliation: Department of Hematology, First Affiliated Hospital, Harbin Medical University, Harbin, China.
authors.forename: J
authors.initials: J
authors.lastname: Hou
authors.forename: Y
authors.initials: Y
authors.lastname: Fu
authors.forename: J
authors.initials: J
authors.lastname: Zhou
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: R
authors.initials: R
authors.lastname: Xie
authors.forename: F
authors.initials: F
authors.lastname: Cao
authors.forename: G E
authors.initials: GE
authors.lastname: Gilbert
authors.forename: J
authors.initials: J
authors.lastname: Shi
mesh_terms: D017304:Annexin A5 / Q000032:analysis* / Q000737:chemistry; D000925:Anticoagulants; D000954:Antigens, Surface / Q000032:analysis* / Q000737:chemistry; D006801:Humans; D008894:Milk Proteins / Q000032:analysis* / Q000737:chemistry; D010718:Phosphatidylserines; D011309:Preservation, Biological
chemical_list: D017304:Annexin A5; D000925:Anticoagulants; D000954:Antigens, Surface; C098942:MFGE8 protein, human; D008894:Milk Proteins; D010718:Phosphatidylserines