Effect of ascorbic acid and thiamine supplementation at different concentrations on lead toxicity in liver

Objective: To investigate the effect of ascorbic acid [vitamin C (VC)] on liver damage parameters in the lead-exposed mice, when given in combination with thiamine [vitamin B1 (VB₁)] at different concentrations. Methods: Sixty-six male mice were randomly assigned into 11 groups (n = 6). Mice in Group I were supplied with only the tap water as the drinking water; mice in Group II were provided with a tap water containing 0.2% lead acetate; mice in Group III-XI were given different dose of VC (140, 420, 1260 mg kg^-1 bw) and VB₁ (10, 30, 90 mg kg^-1 bw) according to 3 x 3 factorial design by oral gavages, along with ingestion of 0.2% lead acetate. After 42 test days, DNA damage of liver cells was assessed using single-cell gel electrophoresis. The apoptosis rate of liver cells was determined by flow cytometry. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in blood and the level of reduced glutathione (GSH) in liver cells were measured based on individual biochemical reactions. Results: Compared with the Group I, sub-chronic lead ingestion (Group II) resulted in a significant decrease of Hb, GSH-P_X, SOD in blood and GSH level in liver cells; lead exposure induced also a significant increase in DNA damage and apoptosis of liver cells (P < 0.05). Supplementation with VC and VB ₁, however, reversed these effects. The best effective combination was VC (420 mg kg^-1 bw) and VB₁ (10 mg kg^-1 bw), followed by the combination of VC (420 mg kg^-1 bw) and VB ₁ (30 mg kg^-1 bw). But no reversion was shown in the combination of the highest combination of VC (1260 mg kg^-1) and VB₁ (90 mg kg^-1). Conclusions: These findings strongly indicated that combination of VC and VB₁ can lessen the damage to liver cells from oxidative stress induce by lead, but the antioxidant effects are dependent on their concentrations.