Fig. 4: Lactate-induced intracellular NADH and ROS signals.

a, b Increase in NAD(P)H autofluorescence (ΔNADH) induced by lactate (Lac in mM, gray) in dispersed glomus cells. Average values (mean ± SEM) in (b) are from: 2.5 Lac (n = 21 cells/6 mice); 5 Lac (n = 27 cells/8 mice); 10 Lac (28 cells/7 mice); 20 Lac (n = 25 cells/4 mice). c Reversible blockade of a lactate (10 mM, gray)-induced rise in intracellular NADH (ΔNADH) by MCT inhibition with AR-C155858 (0.3 μM, light blue). d Box plots representing the distribution of lactate-induced NADH signals under control conditions (gray) and with two different doses (0.3 and 1 μM; light blue) of AR-C155858 (n = 22 cells from 4 mice). Statistical non-parametric tests were used. Calculated mean ± SEM values are: 10 mM lactate: 87.9 ± 11.7; 0.3 μM of AR-C155858: 28.8 ± 6.4; 1 μM of AR-C155858: 3.2 ± 8.5. P values calculated with Mann–Whitney test are indicated. e Inhibition of lactate (10 mM, gray)-induced NADH signal by the application of a short pulse of pyruvate (Pyr, 5 mM, light brown). f Box plots representing the distribution of changes in NADH signals (ΔNADH) induced by lactate (10–20 mM, gray) and following exposure to pyruvate (5–10 mM, light brown) (n = 10 cells from 5 mice). Calculated mean ± SEM values are: 10–20 mM lactate: 22.8 ± 4.0; 5–10 mM pyruvate: −32.3 ± 6.1. The boxplots in (d, f) indicate median (middle line), 25th, 75th percentile (box), and largest and smallest values extending no further than 1.5× interquartile range (whiskers). Data beyond the end of the whiskers (outliers) are plotted individually (gray). The P value calculated with Mann–Whitney test is indicated. g Representative amperometric recordings illustrating the inhibition of lactate (20 mM, gray)-induced secretion in a glomus cell by pyruvate (10 mM, light brown) (similar results were obtained in n = 7 cells from 5 mice). h Representative amperometric recordings illustrating the secretory response to high (5 and 10 mM) lactate (gray) and hypoxia (≈15 mm Hg; pale blue) of glomus cells maintained in physiological resting levels of pyruvate/lactate concentrations (0.1 and 1.4 mM, respectively). i Reversible and dose-dependent increase in mitochondrial matrix ROS induced by lactate (top and bottom; gray) and pyruvate (bottom; light brown) at the indicated concentrations (mM). Note that hypoxia (O₂ tension ≈ 15 mm Hg, pale blue) induces a decrease in matrix ROS. j Average (mean ± SEM) increases in matrix ROS induced by lactate or pyruvate (in mM). Data are from: 2.5 Lac (n = 23 cells/3 mice); 5 Lac (n = 7 cells/2 mice); 10 Lac (n = 30 cells/3 mice); 20 Lac (n = 11 cells/2 mice). Arbitrary units (arb. units). Source data are provided as a Source data file.