| Abstrakt: |
Membranes from platelets obtained from normal human volunteers were isolated for evaluation of their glycoproteins. Values were measured in fresh and stored platelet concentrates at 72 and 96 hr (22 degrees +/- 2 degrees C). Polyacrylamide gels were used to separate the membrane glycoproteins. These were identified as GPI, GPII, GPIII, GPIV, GP77, and GP44. The relative amount of GPI (155,000 daltons) was about 30% less after 72 hr storage than in fresh platelets regardless of the change in the pH of the platelet concentrate. At 96 hr, only an additional 5% loss was seen. The 72 hr value for soluble glycoprotein, glycocalicin, was only 64% of the initial value. GP77 (77,000 daltons) and GP44 (44,000 daltons) became apparent or more prominent with storage. A correlation with pH of the platelet concentrate could be demonstrated for GPI but only with those units in which the pH rose during storage. Density-separated populations of fresh and stored platelets also were studied. They were separated on arabinogalactan (Stractan II) gradients for comparative studies of membrane proteins that might be affected, since platelets become less dense with storage. There was an equal loss of GPI in all populations. However, the change was most striking in the least dense (lightest) fraction because these cells started with 20% less GPI when fresh than did heavier cells. The smallest glycoprotein, GP44, was always present in the lightest platelets after storage, whereas only 40% of the concentrates showed GP77, in small amounts, associated with heavy platelets. Alterations in the membranes of platelets stored as platelet concentrates could result in their functional impairment and loss viability. |
