Glycogen distribution in rat blood platelets.

In rat blood platelets, glycogen particles have been observed in masses contiguous to the open channel system as well as in masses or individual particles scattered throughout platelet hyaloplasm. Rat platelets showed a glycogen distribution in relation to the open channel system in approximately one-third of all platelets seen in randomly selected photomicrographs. The glycogen particles had a mean diameter of 256 A, and the density of glycogen deposits was similar to that observed in human platelets. Glycogen related to the open channel system was seen in proximity to granular structures and frequently was membrane bound. Addition of thrombin, ADP or collagen to platelet-rich plasma, as well as storage of platelets at 21 C, was associated with a loss of glycogen in sites adjacent to the open channel system, but many dispersed glycogen particles appeared to be preserved. The collection of platelets in ethylenediamine tetracetic acid and chilling of platelets reduced the number of glycogen particles contiguous to the open channel system but did not entirely eliminate those glycogen deposits. Glycogen in human platelets apparently has not been observed in a similar relationship to granules and the open channel system. The observations were consistent with the hypothesis that open channel system-related glycogen is more labile in the presence of stimuli for the release reaction and glycogenolysis than is diffusely distributed glycogen.