The Effects of Thymoquinone on Semen Quality in the Diazinon Exposed Rats

Exposure to organophosphate pesticides, including diazinon, can lead to increased production of free radicals and decreased cellular antioxidant capacity and male infertility. Thymoquinone (TQ) is an active component of Nigella sativa with well documented antioxidant effects. This study evaluated the effects of thymoquinone on oxidative stress induced by exposure to diazinon and semen quality in male rats.

Twenty-eight male Wistar rats weighing 200-300 g were randomly divided into four groups (n=7, each). The first (control) group received a single intraperitoneal (i.p.) injection of olive oil (medication vehicle). Testicular toxicity was induced in rats of the second and third groups by a single injection of diazinon (20 mg/kg, i.p.). Also, the animals of the second and third groups received the vehicle of TQ (olive oil) or TQ (10 mg/kg/day, i.p.), respectively, for five consecutive days starting 3 days before diazinon administration. The fourth group of animals received thymoquinone (10 mg/kg/day) for five consecutive days without induction of diazinon toxicity. Thirty-six hours later, semen quality was assessed for motility, morphology, and viability of sperms in addition to measurement of malondialdehyde (MDA) level in testis tissue.

The results showed that the sperm motility significantly decreased and MDA level significantly increased (P<0.0001) after diazinon exposure whereas thymoquinone increased sperm motility and decreased MDA level (P<0.0001) in testis tissue after exposure to diazinon as compared to the control group.

Since diazinon increases lipid peroxidation in sperm plasma membrane through production of free radicals, it can be concluded that administration of thymoquinone as an antioxidant can prevent diazinon toxicity in testis tissue of rats, and improve the quality of semen.