Structured light microscopy of lactate-stimulated proton transport in rat ventricular myocytes labeled with WGA-pHRho. (A) A ∼750-nm illuminated z-plane of a WGA-pHRho–labeled ventricular myocyte ∼2 μm above the coverslip focal plane. (B) Time course of 10 mM lactate perfusion before (red) and after addition of 50 nM AR-C155858 (gray). Plotted data are mean + SEM (shading) for clarity (n = 6 cells); data were collected at 1 Hz. (C) Pseudocolor image depicting the eroding pixel (5 px) analysis to generate the four annuli. (D) Changes of ΔF/F₀ before, during, and after perfusion of 10 mM lactate at each annulus (A0–A3). (E) Pixel intensity histogram of the four annuli (area normalized) for cell shown in A. (F) Average maximal |ΔF/F₀| upon wash in (solid bars) and wash out (open bars) of 10 mM lactate for nine cells. One-way ANOVA (Bonferroni's multiple comparison test) was used to determine significance (*, P < 0.05; **, P < 0.01; ***, P < 0.001). Error bars represent SEM.