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

Abstract

Background: 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. Objectives: The present study aimed to investigate the effect of nitrate and vitamin C on the expression of type-IV collagen in rat kidney. Methods: 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. Results: 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). Conclusions: 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.