Functional platelets after storage in vitro for 15--21 days.

Blood platelets are notoriously difficult to preserve in vitro for long periods of time. Despite many efforts to solve the problem and improve conditions for storage, platelets lose their ability to respond to aggregating agents after 72--96 hours and are routinely discarded by blood banks after three days if not used for transfusion. The present study has evaluated the influence of raising the pH of the anticoagulant used to collect blood on the functional viability of platelets during storage at room temperature. Twenty-four samples of C-PRP were followed for 15 days and 12 samples for 21 days. Although platelet counts fell steadily during the 3-week storage period, a significant proportion of the cells remained viable. After 5--10 days the platelets responded as well to threshold concentrations of ADP and sodium arachidonate (SA) as on Day 0, and reactions to the same agents on Day 15 were nearly as impressive. Even on Day 21, responses to ADP and SA could still be elicited. Biochemical studies on samples stored for 15--21 days revealed normal levels of serotonin after 2 weeks and a fall of less than 30% after 3 weeks. The ability of the cells to convert 14C-arachidonic acid into thromboxane B2 was well maintained over the 3-week period. Adenine nucleotide levels fell 25% over 15 days and over 50% by 21 days, but the capacity of the cells to take up 14C-adenine and convert it to AMP, ADP, and ATP was increased, and ATP/ADP ratios were not greatly different from those on Day 0. Physical changes were apparent in most platelets by Day 15. However, 5--20% of platelets in 15--21-day-old samples were discoid in shape and contained circumferential bands of microtubules and small amounts of glycogen. The findings suggest that high pH during collection of blood, preparation of C-PRP, and early phases of storage may foster long-term preservation of viable platelets in vitro.