Figure 2. Succinate Enhances Export of Malate in Eyecups.

(A) Rate of TCA cycle metabolite release by eyecups incubated in 5 mM ¹²C-glucose. Media samples were taken at 30, 60, and 90 min (n = 9 eyecups, 3 per time point; error bars indicate SEM). (B) Labeling schematic showing TCA cycle isotopomers produced by eyecups supplied with ¹²C-glucose and U-¹³C-succinate. For simplicity, only isotopomers originating from either metabolite produced in a single turn of the TCA cycle are shown. (C) Rate of TCA cycle metabolite release by eyecups incubated in 5 mM ¹²C-glucose + 2 mM U-¹³C-succinate for 60 and 90 min. The rate at which succinate is consumed by eyecups during incubation is shown on the right (n = 6 eyecups, 3 per time point; error bars indicate SEM). (D) Rate of TCA cycle metabolite release by eyecups incubated in 5 mM ¹²C-glucose + 50 μM U-¹³C-succinate for 30 min. The rate at which succinate is consumed by eyecups during incubation is shown on the right (n = 3 eyecups; error bars indicate SEM).