title: Subcellular localization of the heparin-neutralizing factor in blood platelets.
abstract: 1. The distribution of the heparin-neutralizing factor (platelet factor 4, PF4) in subcellular organelles of blood platelets of rabbits and man was investigated. 2. In both species the organelles storing 5-hydroxytryptamine (5-HT storage organelles) contained only trivial amounts of PF4. 3. In contrast, the content of PF4 was highest in the subcellular fractions rich in alpha-granules. 4. In conclusion, PF4 is probably localized in the alpha-granules and therefore the platelets contain at least two types of organelles (5-HT organelles and alpha-granules) capable of releasing their contents in response to the same stimuli, such as exposure to collagen, thrombin, etc.
mesh_terms: D000818:Animals; D001779:Blood Coagulation Factors / Q000032:analysis*; D001792:Blood Platelets / Q000032:analysis* / Q000648:ultrastructure; D006801:Humans; D010978:Platelet Factor 4 / Q000032:analysis*; D011817:Rabbits; D012701:Serotonin / Q000032:analysis; D013347:Subcellular Fractions / Q000032:analysis
chemical_list: D001779:Blood Coagulation Factors; D012701:Serotonin; D010978:Platelet Factor 4