Diabetes mellitus- induction: Effect of different streptozotocin doses on male reproductive parameters

Diabetes mellitus (DM) is reported to be involved in male reproductive impairment, and its impact is evident in the increased prevalence of infertility. Various studies have reported that a single parenteral injection of <40 mg/kg Streptozotocin (STZ) is ineffective in ablating pancreatic β-cells and creating a rat model to investigate the effect of DM on the male reproductive system. This study therefore aims to validate these claims. Adult male Wistar rats received either a single intraperitoneal injection of STZ (30 mg/kg or 60 mg/kg) or saline (0.9%, Control). Diabetes was confirmed after 72 h if plasma glucose levels were ≥14 mmol/L. Body weight, glucose level, fluid and food intake were measured weekly. Animals were sacrificed after 8 weeks of treatment by an overdose of sodium pentobarbital (160 mg/kg body weight). The testis and epididymis were harvested and weighed prior to preparation for histological evaluation. Epididymal sperm morphology was analysed using computer aided sperm analysis (CASA). STZ60 animals presented with significantly lower body weights compared to both control and STZ30 groups. Animals in both STZ30 and STZ60 groups showed decreased normal sperm morphology compared to control. Histological evaluation of the testes showed a decrease in the number of spermatozoa in the seminiferous tubules of animals in the STZ30 and STZ60 groups compared to control. A complete absence of spermiogenesis was observed in the seminiferous tubules of STZ60 animals. These findings prove that an STZ concentration of 30 mg/kg, which is much lower than the reported 40 mg/kg, has adverse effects on the male reproductive system via its diabetogenic effect and can therefore be used to study the impact of DM on male fertility.