Fig 11. Analysis of back exchangeability of radiolabeled SM or POPC introduced into A549 cells by lipid exchange.

(A) Back exchangeability of ³H-SM immediately after exchange (0) or 2 h recovery after exchange with 1:1 bSM:POPC. (B) Back exchangeability of ¹⁴C-DOPC immediately after exchange (0) or 2 h recovery after exchange with POPC. The p value for the significance of the difference at 0 and 2 h is 0.04. Back exchangeability is given by the % of radiolabeled lipid removed after a 1h second lipid exchange step in the presence of MαCD using unlabeled lipid. Exchange was carried out in 3.5 cm diameter plates with 1 ml of lipid plus 40 mM MαCD (See Methods for details). Recovery was carried out at 37°C in the same plates with 1.5 ml of complete growth medium. Mean and standard deviations from three experiments are shown.