L-carnitine decreases glycolysis in liquid-stored platelets

BACKGROUND: The platelet storage lesion is characterized metabolically by a pH decrease associated with lactic acid generation; a change in platelet m orphology from discoid to spherical, a diminished response to in vitro chal lenge tests, such as the hypotonic shock response (HSR) and extent of shape change (ESC); increased surface P-selectin expression; and decreased in vi vo recovery and survival. Altering storage conditions to improve these meas ures could allow for extension of the duration of in vitro storage. STUDY DESIGN AND METHODS: ABO-identical paired platelet concentrates were p ooled and then equally divided into two plastic bags. Either L-carnitine (L C) or an equal volume of saline (control) was added to one container of eac h pair. Platelets were stored at 20 to 24 degreesC for 5 to 10 days or at 1 to 6 degreesC for 5 days at various concentrations of LC between 0.1 and 1 5 mM. At the end of storage, pH, glucose consumption, lactate generation, H SR, ESC, and surface P-selectin expression were measured. In different expe riments, paired platelet concentrates were spiked with a Staphylococcus epi dermidis suspension in the presence and absence of L-carnitine dt a concent ration of 5 mM. RESULTS: At 20 to 24 degreesC and concentrations of LC between 0.1 and 5 mM there was evidence of better pH preservation, less glucose consumption, an d less lactate generation. Only with storage beyond 5 days was a difference : present in either surface P-selectin expression or HSR. An L-carnitine co ncentration of 5 mM appeared optimal. L-carnitine did not enhance the growt h of bacteria after 7 to 8 days of storage. CONCLUSION: LC at 5 mM may improve the quality of platelet concentrates tha t are stored beyond 5 days. There was no indication that LC at this concent ration would promote bacterial growth. It may be a useful additive to plate let preservation.