PMC

Spectral changes of TDO in the presence of ascorbate (A) and sodium hydrosulfite (B). The baseline was adjusted as described in . Traces in A illustrate the spectrum of TDO in the absence of ascorbate (trace 1) and the spectral changes of TDO in the presence of 1 (trace 2), 5 (trace 3), and 10 mM of ascorbate (trace 4). Traces in B show the spectrum of TDO in the absence of sodium hydrosulfite (trace 1) and the spectral changes of TDO at 3.0 min after addition of 0.2 (trace 2), 0.5 (trace 3), and 1.0 mM of sodium hydrosulfite (trace 4).

Menadione reduction reactions using sodium hydrosulfite.

Effect of ascorbate and sodium hydrosulfite on TDO activity. Freshly prepared tryptophan and ascorbate or sodium hydrosulfite solutions were first mixed and the reaction was initiated by the addition of TDO. Spectral change at 321 nm was monitored continuously for 40 min at 35°C. A: Traces illustrate absorbance increases at 321 nm in TDO and tryptophan reaction mixtures in the absence of ascorbate (trace 1), in the presence of 0.1 (trace 2), 1.0 (trace 3), and 5 mM (trace 4) of ascorbate, and in the presence of 5 mM ascorbate plus 500 U of both superoxide dismutase and catalase (trace 5). B: Traces show absorbance increases at 321 nm in TDO and tryptophan reaction mixtures in the absence of sodium hydrosulfite (trace 1) and in the presence of 0.05 (trace 2), 0.1 (trace 3), 0.2 (trace 4), 0.4 (trace 5), and 1.0 mM sodium hydrosulfite (trace 6). The total volume of the reaction mixture was 1 ml, the amount of TDO was 10 μg, and the concentration of tryptophan was 10 mM.

(A) Normalized cell index and (B) AUC calculations of neonatal rat cardiomyocytes after exposure to sodium hydrosulfite. Data are presented as the mean ± standard error of the mean. *P<0.01 vs. Control; ^#P<0.01 vs. all other groups. Control, normal media group without sodium hydrosulfite; AUC, area under the time-course curve.