Fig. 4.

Functional analysis of cryopreserved HDL. HDL isolated by density gradient ultracentrifugation was stored at −20°C or −70°C in the presence or absence of the cryoprotectants, sucrose (2–10%) or glycerol (10–50%), for up to 110 weeks. Samples from four healthy donors were pooled and aliquots were analyzed for their ability to promote cholesterol efflux (A–E) and for their HDL-associated paraoxonase 1 activity (F–J) at indicated time points. The dashed lines indicate the control value measured right after the isolation of HDL and were used for normalization to 100%. Results represent the combined analysis of two independent experiments performed in triplicate. *P < 0.05 versus control.