Fig. 1

Hypoxia blunts H₂O₂ generation, but re-oxygenation regains it in HyPer1 transgenic zebrafish embryo. (A) Schematic illustration of fluorometric features of the HyPer1, a specific H₂O₂ sensor. (B) Experiment summary. The transgenic zebrafish embryos harboring ubiquitous HyPer1 expression were used. The embryos were placed in distinct environments (constant normoxia, hypoxia, and re-oxygenated normoxia) and subjected to imaging analysis. (C, D) Changes in H₂O₂ levels in zebrafish embryos during the transition from normoxia to hypoxia (C) or from hypoxia to normoxia (D). Transgenic fish expressing HyPer1 under the control of a ubiquitin gene promoter (ubi) were allowed to develop normally for up to 24 hr post-fertilization (hpf), and fluorescence signals were detected approx. 20 and 10 min before each treatment. After that, the rearing water of the embryos was replaced with hypoxic (C) or normoxic (D) water, and the images were timelapse photographed every 10 min for 2.5 hr after the transitions. The fluorescence intensity was analyzed in each image. The timing of the red arrows indicates the transition. The HyPer1 signal was calculated relative to the signal intensity of the first photo. Data are mean ± SE of 7 independent experiments. Values marked with different letters (a, b, c) are significantly different from each other (P<0.05), but values marked with common letters (b and bc; bc and c) are not significantly different from each other (P>0.05).