Restoration of Ovarian Function and Hormonal Balance by Vernonia calvoana in Heavy-Metal-Intoxicated Rats

Abstract

Heavy metal contamination in groundwater, particularly in the Niger Delta, induces oxidative stress and endocrine disruption. This study aimed to evaluate the restorative potential of Vernonia calvoana extract fractions on hormonal parameters and ovarian histoarchitecture in female Wistar rats chronically exposed to heavy-metal-laden water sourced from Azikoro, Bayelsa State. Methodology involved assigning thirty female rats to six groups: normal control, negative control (Azikoro well water), positive control (Vitamin C), and three treatment groups receiving 400 mg/kg of V. calvoana aqueous, methanol, and n-hexane fractions. After 30 days of oral treatment, serum concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, and progesterone were quantified via ELISA, and ovarian tissues were examined histopathologically. Results showed Azikoro well water contained toxic levels of metals exceeding WHO limits, Iron (3.826 ± 1.05mg/L), Cadmium (0.046 ± 0.00mg/L), Nickel (0.840 ± 0.00mg/L), Lead (0.059 ± 0.00mg/L), and Cobalt (0.123 ± 0.00mg/L). Exposure significantly suppressed hormonal levels in negative control group compared to normal control group at 95% confidence level: FSH (6.03 ± 1.13 vs 15.00 ± 1.73 mIU/mL), LH (7.00 ± 0.29 vs 20.00 ± 2.89 mIU/mL), progesterone (35.33 ± 0.33 vs 50.00 ± 9.24 ng/mL), and estradiol (22.00 ± 1.53 vs 25.00 ± 0.58 pg/mL). The aqueous fraction exhibited superior restorative efficacy, increasing FSH to 11.67 ± 1.48 mIU/mL, LH to 16.00 ± 0.29 mIU/mL, and progesterone to 42.00 ± 1.15 ng/mL. Histopathology confirmed that while heavy metals caused stroma degradation, aqueous treatment restored mature Graafian follicles and viable oocytes. In conclusion, Vernonia calvoana, especially its aqueous fraction, effectively mitigates heavy-metal-induced reproductive toxicity by normalizing hormonal profiles and restoring ovarian structural integrity.