Figure 1. Endothelial cells import exogenous lactate.

(A and B) HUVECs were incubated during 6-h with 10 mM of ¹³C-methy-labeled sodium lactate (left panels) or 10 mM of ¹²C sodium lactate (right panels). ¹³C-lactate was detected using nuclear magnetic resonance (NMR) in cell lysates. (A) In ¹³C NMR spectra, a ¹³C-Lactate peak is detected at 19 ppm. (B) In ¹H NMR spectra, the methyl doublets at 1.56 and 1.30 ppm arise from ¹³C-lactate whereas the doublet at 1.43 ppm arises from a coincidental overlap of endogenous ¹²C-Lactate and threonine. (C) HUVECs were incubated with 10 mM sodium L-lactate. L-Lactate was detected using an enzymatic assay in the lysate of cells collected at different time points. *p<0.05; n = 4. Error bars reflect mean ± SEM.