title: A radioimmunoassay for thrombospondin, used in a comparative study of thrombospondin, beta-thromboglobulin and platelet factor 4 in healthy volunteers.
abstract: A radioimmunoassay was developed for the platelet alpha-granule protein thrombospondin; concentrations of thrombospondin as low as 3 ng ml-1 could be measured. There was no interference from other components of human biological fluids and no crossreactivity with beta-thromboglobulin (beta-TG) or platelet factor 4 (PF4). Plasma samples were stable when stored at -20 degrees C. Normal human plasma contained 105.0 +/- 31.0 ng thrombospondin ml-1 compared with beta-TG concentrations of 37.2 +/- 10.9 ng ml-1 and PF4 concentrations of 14.7 +/- 10.1 ng ml-1 when samples were carefully taken into a platelet inhibitor cocktail and processed at 0-4 degrees C. Release of thrombospondin during clotting of blood occurred at the same time as that of beta-TG and PF4 and resulted in a serum concentration of 17.5 +/- 5.5 micrograms ml-1. Assay of whole blood gave a platelet thrombospondin content of 89.1 +/- 28.3 ng/10(6) platelets. The concentration in normal urine fluctuated widely from 3 to 22.5 ng ml-1, and was unrelated to urine flow. The half-life of thrombospondin in vivo was about 9 h, much longer than that of either beta-TG or PF4. Unlike PF4, it was not released into the blood following an intravenous heparin injection. Bovine, ovine, canine and porcine sera contained thrombospondin which crossreacted immunologically with the human molecule; these species would be suitable animal models for the study of thrombospondin and its value as a platelet release marker.
mesh_terms: D000328:Adult; D000818:Animals; D001609:Beta-Globulins / Q000032:analysis*; D001779:Blood Coagulation Factors / Q000032:analysis*; D002417:Cattle; D003429:Cross Reactions; D004285:Dogs; D005260:Female; D006023:Glycoproteins / Q000097:blood* / Q000652:urine; D006168:Guinea Pigs; D006207:Half-Life; D000882:Haplorhini; D006493:Heparin / Q000008:administration & dosage; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D008297:Male; D051379:Mice; D008875:Middle Aged; D010978:Platelet Factor 4 / Q000032:analysis*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D013045:Species Specificity; D019699:Thrombospondins; D001620:beta-Thromboglobulin / Q000032:analysis*
chemical_list: D001609:Beta-Globulins; D001779:Blood Coagulation Factors; D006023:Glycoproteins; D007106:Immune Sera; D019699:Thrombospondins; D001620:beta-Thromboglobulin; D010978:Platelet Factor 4; D006493:Heparin