A method for the isolation of α-granules from human platelets

A method for the isolation of α-granules is described. A two-step French pressure cell homogenization procedure which directly produced an organelle concentrate suited for loading on density gradients was developed. The procedure was optimalized with respect to recovery of intact α-granules. The organelle homogenate was loaded to 17.5 – 27.5% metrizamide gradients and centrifuged. Organelle aggregate formation was minimized by controlling the ionic conditions and the shape of the gradient. The α-granules were separated from lysosomes and dense bodies, but overlapped with the mitochondria. The α-granules were recovered from the gradient in order to omit the major amount of mitochondria from the final preparation. A washing procedure which introduced a minimum of α-granule adhesivity and fragility is presented.