Fig. 4. Effects of antioxidants on the viability of G. dibranchiata erythrocytes exposed to H₂S in vitro. (A–D) Epifluorescence micrographs of cells in incubation buffer that were exposed for 2 h to air (A) and 0.32% H₂S (B), and cells in incubation buffer with GEE (glutathione ethyl ester) (3 mmol l^–1), NAC (N-acetylcysteine) (1.0 mmol l^–1), ASC (L-ascorbic acid) (0.10 mmol l^–1), Tempol (4-hydroxyl-2,2,6,6-tetramethylpiperidine-1-oxyl) (3.0 mmol l^–1) or Trolox (6-hydoxy-2,5,7,8-tetramethylchroman-2-carboxylic acid) (0.10 mmol l^–1) that were then exposed for 2 h to air (C) or 0.32% H₂S (D), followed by labeling with calcein (green) and propidium iodide (PI; red). (E–F) Quantitative analysis of calcein labeling (E) and total PI labeling (F) in cells incubated with various concentrations of antioxidant (0–3.0 mmol l^–1 GEE, 0–1 mmol l^–1 NAC, 0–0.1 mmol l^–1 ASC, 0–3.0 mmol l^–1 Tempol or 0–0.1 mmol l^–1 Trolox) and exposed for 2 h to 0–3.2% H₂S. N=5. Results of statistical analysis presented in Table 1.