L-carnitine improves pH and decreases surface phosphatidylserine expression in extended stored apheresis platelets

Extension of the storage period of apheresis platelets to seven or ten days may be possible with the implementation of screening for bacteria. This, however, may impair platelet quality, and additive compounds that improve storage parameters would be desirable. Apheresis platelets were harvested using the Cobe LRS device. Part of the product was aliquoted into two CLX bags, 60 ml into each, on day 0. L-carnitine (LC) to a final concentration of 5 mM was added to one container and saline to the other. pH, morphology score, and surface expression of phosphatidylserine were measured on day 1, and, in addition, hypotonic shock response (HSR) and the extent of shape change (ESC) on days 5, 10, and 13. Differences between test and controls were analyzed using paired t-tests. The addition of LC improved pH by day 5, but was more evident by days 10 and 13. By day 10, significant differences (<0.01) were observed in pH (6.54 +/- 0.3 vs. 6.75 +/- 0.3), lactate (176 +/- 31 vs. 150 +/- 24 mg %), morphology score (213 +/- 27 vs. 229 +/- 35) and ESC (7 +/- 6 vs. 11 +/- 6). Percent surface phosphatidylserine expression was less in the LC treated platelets (16 +/- 7 vs. 12 +/- 4, P<0.03). Much of the benefit observed was attributable to improved parameters in some donors. LC improves the quality of extended stored apheresis platelets.