title: Sphingosine 1-phosphate release from platelets during clot formation: close correlation between platelet count and serum sphingosine 1-phosphate concentration.
abstract: BACKGROUND
  Sphingosine 1-phosphate (Sph-1-P), abundantly stored in platelets and released extracellularly upon activation, plays important roles as an extracellular mediator by interacting with specific cell surface receptors, especially in the area of vascular biology and immunology/hematology. Although the plasma Sph-1-P level is reportedly determined by red blood cells (RBCs), but not platelets, this may not be true in cases where the platelets have been substantially activated.
  
  
  RESULTS
  We measured the Sph-1-P and dihydrosphingosine 1-phosphate (DHSph-1-P) levels in serum samples (in which the platelets had been fully activated) from subjects with (n = 21) and without (n = 33) hematological disorders. We found that patients with essential thrombocythemia exhibited higher serum Sph-1-P and DHSph-1-P concentrations. The serum Sph-1-P concentration was closely correlated with the platelet count but was very weakly correlated with the RBC count. Similar results were obtained for DHSph-1-P. The serum Sph-1-P and DHSph-1-P levels were inversely correlated with the level of autotaxin (ATX), a lysophosphatidic acid-producing enzyme. A multiple regression analysis also revealed that the platelet count had the greatest explanatory impact on the serum Sph-1-P level.
  
  
  CONCLUSIONS
  Our present results showed close correlations between both the serum Sph-1-P and DHSph-1-P levels and the platelet count (but not the RBC count); these results suggest that high concentrations of these sphingoid base phosphates may be released from platelets and may mediate cross talk between platelet activation and the formation of atherosclerotic lesions.
authors: Department of Clinical Laboratory, The University of Tokyo Hospital, Tokyo, Japan.
authors: Yoshikazu
authors: Y
authors: Ono
authors: Makoto
authors: M
authors: Kurano
authors: Ryunosuke
authors: R
authors: Ohkawa
authors: Hiromitsu
authors: H
authors: Yokota
authors: Koji
authors: K
authors: Igarashi
authors: Junken
authors: J
authors: Aoki
authors: Minoru
authors: M
authors: Tozuka
authors: Yutaka
authors: Y
authors: Yatomi
mesh_terms: D000741:Anemia, Aplastic / Q000097:blood* / Q000473:pathology; D001777:Blood Coagulation; D001792:Blood Platelets / Q000378:metabolism* / Q000473:pathology; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D006801:Humans; D008246:Lysophospholipids / Q000097:blood* / Q000378:metabolism; D010727:Phosphoric Diester Hydrolases / Q000097:blood; D015539:Platelet Activation; D010976:Platelet Count; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000097:blood* / Q000473:pathology; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D013920:Thrombocythemia, Essential / Q000097:blood* / Q000473:pathology; D014280:Triglycerides / Q000097:blood; D014842:von Willebrand Diseases / Q000097:blood* / Q000473:pathology; D000099189:Lysophospholipase D
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D008246:Lysophospholipids; D010727:Phosphoric Diester Hydrolases; D013110:Sphingosine; D014280:Triglycerides; D000099189:Lysophospholipase D; C060506:sphingosine 1-phosphate