Protein synthesis in human platelets correlation with platelet size

Protein synthesis was investigated in human platelets by measuring incorporation of radio actively labelled amino acids into trichloroacetic acid (TCA) precipitable material. Platelet polysomes were characterized by their sedimentation rate in a sucrose gradient. It was confirmed that platelets synthesize proteins in their cytoplasm and that a part of their polysomes are bound to the skeletal framework. A higher level of protein synthesis was found in a population of small platelets separated on Ficoll (2%-4%) density gradient. Moreover, small platelets contained more polysomes than larger platelets. These results show that small platelets are more active in protein turnover or de novo synthesis. These findings can be related to peripheral maturation of platelets.