Protective Effect of Vitamin C on Protein Expression of Type-IV Collagen Following the Consumption of Nitrate-Containing Drinking Water in Rat Kidney

Evidence shows that chemical fertilizers used for agricultural purposes have high levels of nitrate. These agricultural products consumed by livestock are the most important sources of nitrate. Type-IV collagen, found primarily in the base membrane, is significantly vital for the performance of glomerular base membrane in the kidney. The present study aimed to investigate the effect of nitrate and vitamin C on the expression of type-IV collagen in rat kidney. This empirical research was conducted on 49 Wistar rats in Iran from 2017 to 2018. The sample size was determined using Morgan Table Samples were randomly divided into seven groups: (1) no nitrate (control), (2) nitrate at 10 mg/L, (3) nitrate at 45 mg/L, (4) nitrate at 200 mg/L, (5) nitrate (10 mg/L) + vitamin C (20 mg per 100 g of body weight), (6) nitrate (45 mg/L) + vitamin C (similar amount), and (7) nitrate (200 mg/L) + vitamin C (similar amount). After 91 days, the content of type-IV collagen in the kidney tissue was determined using the immunohistochemistry (IHC) protocol. The expression of type-IV collagen gene was detected by real-time polymerase chain reaction (RT-PCR) in all groups. There was no significant difference among the groups of 1-3 (4.55 ± 0.51, 4.7 ± 0.47, 3.6 ± 0.5, P > 0.05) in terms of type-IV collagen. However, the obtained results of group 4 indicated a significant reduction in the content of type-IV collagen (1.25 ± 0.44), compared to the control group (4.55 ± 0.51, P = 0.000). In terms of vitamin C consumption, the groups of 5 (3.45 ± 0.51) and 6 (3.4 ± 0.5) did not differ significantly from the control group (4.55 ± 0.51, P > 0.05). Nonetheless, the severity of response to anti-type-IV collagen antibody significantly increased in group 7 (3.55 ± 0.6) compared to group 4 (1.25 ± 0.44, P < 0.05). The investigated doses of nitrate in drinking water (up to 45 mg/L) had no significant effect on the content of type-IV collagen. On the other hand, the excessive concentrations of nitrate limited the distribution of type-IV collagen and led to potential side effects on the glomerular base membrane. Moreover, vitamin C had no significant effect on 10 and 45 mg/L doses of nitrate. Nevertheless, 200 mg/L dose of nitrate improved the destructive effects of type-IV collagen on the kidney.