Limited metabolic effect of mononuclear cells in platelet storage.

Platelet concentrates (PC) were prepared by platelet apheresis to obtain a low (< 0.1 x 10(9)/l, PC A) and high (2-9 x 10(9)/l, PC B) concentration of white cells from the same donor. The mean platelet count (+/- SD) of the PC were 1000 +/- 50 x 10(9)/l. During storage 71-96% of the white cells were mononuclear. A portion of red cells from each donor was also stored under the same conditions. The results of the PC were corrected for the influence of contaminating erythrocytes. During the whole storage period pO2 was significantly lower in PC with high white cell count, p < 0.05 and the concentration of ATP significantly higher, p < 0.01 on day 0, 3 and 5, p < 0.05 on day 1 and 7. There were no significant differences in pH, pCO2, production of lactate or consumption of glucose. In another 17 apheresis PC leukocyte viability was assessed by exclusion of 0.05% trypan blue on days 5 and 7; 90 +/- 3 and 88 +/- 4% respectively of the leukocytes remained viable; 87 and 96% respectively were mononuclear cells. In a third series of PC prepared with extra high white cell count (0.4-1.6 x 10(9)/unit) was oxidative phosphorylation maintained and pH remained between 6.80 and 7.16 in 12 of 16 PC after 5 days of storage. The presence of mononuclear cells in PC does not impair the maintenance of platelet ATP production and oxidative phosphorylation unless the platelet concentration is high enough almost to exceed the oxygen diffusion capacity of the bag. If so, the white cells significantly contributed to the oxygen deficit and pH and ATP rapidly decreased due to anaerobic metabolism. We conclude that mononuclear cells can be stored in plasma together with platelets at aerobic conditions for 7 days with maintained concentration of platelet ATP.