Effect of Sub-chronic Oral Mercuric Chloride (HgCl₂) Exposure on Sperm Parameters and Testicular Architecture of Male Wistar Rats

Mercury exposure is an environmental toxic factor that can impair male reproductive function. The duration of exposure plays a critical role in determining the severity of testicular damage and the progression of spermatogenic impairment. This study ​ ​evaluated the time-dependent effects of subchronic oral mercuric chloride exposure on male reproductive parameters. This experimental study employed a post-test only control group design and involved 25 male Wistar rats, randomly allocated into five groups (n=5): a control group and four treatment groups receiving oral mercuric chloride (HgCl₂) 0.4 mg/kg body weight for 7, 14, 21, and 28 days. The evaluated parameters included sperm concentration, motility, viability, and morphology, as well as Leydig cell count and seminiferous tubule diameter. ​ ​Data were analysed using one-way ANOVA or Kruskal–Wallis tests followed by appropriate post hoc analyses. ​Significant differences were observed among groups for all parameters (p < 0.05)​​ ​. Sperm viability and Leydig cell counts were the most sensitive parameters, showing significant reductions as early as 7 days of exposure. Sperm morphology declined significantly after 14 days, while sperm motility decreased significantly at 21–28 days of exposure. Sperm concentration showed significant reduction only after 28 days of exposure. The seminiferous tubule ​​diameter exhibited a biphasic pattern, characterized by early expansion followed by degenerative narrowing, a pattern not extensively documented in previous subchronic mercury studies. In conclusion, subchronic mercuric chloride exposure induces duration-dependent reproductive toxicity, with sperm viability and Leydig cells as early sensitive biomarkers and a novel biphasic pattern in testicular structural changes.