Fig. 1: Methylene blue increases basal OCR and mitochondria membrane potential (ΔΨm) in 1 and 2 dpf zebrafish embryos.

A Schematic representation detailing the experimental design. B Table showing the concentrations of MB with references. C Scheme of the MITO stress test OCR measurements. D OCR measurements of 1 dpf zebrafish embryo after MB exposure. n = 6–7 (Each biological replicate is represented by a single embryo). E Plots investigating relationships between basal respiration and different MITO stress test endpoints in control and different MB exposure concentrations. R² and P values are provided. F The ratio of green/red (TRITC/GFP) fluorescent intensity and representative images of 2 dpf zebrafish embryos stained with JC-10 fluorescent stain after exposure to multiple concentrations of methylene blue. n = 4–5 (Each biological replicate is represented by a single embryo). The data were graphed as violin plots showing the mean (symbol: +), the median represented by a line in the middle, the upper and lower quartile range indicated by the dotted lines, and the outline of the violin plot illustrates the kernel probability density. Asterisks indicate *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001. (Magnification 10x; scale bar, 300 μm).