Platelet Membranes, Eicosanoid Biosynthesis and Putative Endogenous Calcium Ionophores

Abstract

In order to facilitate our understanding of the biochemical events that accompany surface membrane receptor activation, generation of second messengers and the sequence of metabolic events involved in mobilisation of arachidonic acid (AA) from membrane phospholipids; it is important to be able to separate subcellular fractions representative of surface membrane (SM) and membranes of intracellular origin (IM). In the case of the platelet, such preparations have proved exceedingly difficult to achieve. The isolation and characterisation of cell membranes representative of surface and intracellular origin presents the biochemist with a number of problems. Thus, in secretory cells surface membranes may contain similar structural/functional proteins, antigenic determinants, marker enzymes and other physicochemical prqperties similar to intracellular membranes, albeit in different proportions or orientations. In relation to the platelet, problems arise due to the small size of this cell and its resistance to breakage by mechanical stress forces and further by the requirement to prevent aggregation and degranulation during the preparative procedures.