the 5-hydroxytryptamine ( 5ht ) -system of human blood platelets consists of a relatively specific uptake mechanism for 5ht at the plasma membrane , intracellular storage organelles ( dense bodies ) , a metabolizing enzyme ( monoaminoxidase b ) and a 5ht2-receptor whose stimulation leads to activation of the phosphatidylinositide turnover , a rise in free cytoplasmic ca2+ , phosphorylation of proteins and a shape change reaction .
C0007603
plasma membrane
C0010834
cytoplasmic