Fig. 2.

Glutamine contributes to the TCA cycle in HCEC. (A) Schematic illustration of proposed glutamine metabolism in corneal endothelium; (B) Ammonia release is dependent on glutamine concentration in HCEC; (C) GC–MS results show ~ 50% of carbons in the TCA intermediates are from glutamine. ¹³C is illustrated as red dot, whereas ¹²C is gray dot. Cells were cultured for 12 h in 4 mM U-¹³C₅-glutamine and 13.9 mM unlabeled glucose in experimental group (blue bars), whereas 4 mM unlabeled glutamine and 13.9 mM unlabeled glucose in control (gray bars). The isotopologue distributions were corrected based on the natural abundance of elements (gray bars), and the labeled fraction (blue bar) is the contribution of each isotopologue to the total abundance of all the isotopologues.