Freezing of human spermatozoa is done to increase the success of assisted reproductive techniques (Agarwal & Majzoub, 2017). In the freezing method, intracellular ice crystal formation and the concentration of solute are problematic, and the survival of frozen cells depends on the type of cell and freezing rate (Tomás et al., 2019). One way to avoid damage by forming ice crystals is to use the vitrification method (Arav et al., 2018). In the vitrification method, freezing is performed by immersing the samples directly into the liquid nitrogen tank (Isachenko et al., 2018). This method reduces ice crystal formation and intracellular injuries (Adib et al., 2018). Vitrification is delivered in less time than conventional sperm freezing methods and is also safer and less costly (Horta et al., 2017; Spis et al., 2019). Evidence has shown that in semen, ROS are produced in the freezing and thawing processes. Although the average level of ROS can regulate sperm functions when it exceeds the detoxification level, it leads to oxidative stress (Lone et al., 2018). Free radicals from oxidative stress can disrupt motility after thawing, viability, cell membrane, mitochondrial membrane potential, DNA fragmentation, intracellular enzymatic activity, sperm function and fertility (Bustamante Filho et al., 2018; Zhang et al., 2019). Recent studies have indicated that ultra-rapid freezing reduces destructive effects on sperm

Background: Tamsulosin is an inhibitory factor of alpha-adrenergic receptors that is used for relieving of the clinical symptoms and management of acute urinary retention. Objective: The aim of this study was to evaluate the effects of tamsulosin on the endocrine axis and testicular tissue in adult male rats. Materials and Methods: In this experimental study, 30 adult male Wistar rats (weighing 250-300 gr) were divided into three groups: 1) control (received distilled water), 2) experimental 1 (received 0.2 mg/kg/day tamsulosin) and 3) experimental 2 (received 0.4 mg/kg/day tamsulosin) through oral gavage for 28 days. Serum hormones level and testicular histopathology were evaluated at the end of the experiment. Results: In this study, the testicular weight decreased significantly in the experimental groups compared to the control group. A significant decrease was seen in testicular weight (p = 0.004) and the number of Leydig cells in tamsulosin-treated groups (p = 0.012). Tamsulosin improved the hormone profile in experimental groups. Also, higher dose of tamsulosin significantly changed the number of Leydig, spermatogonia cells, the thickness of germinal layer, and the diameter of the seminiferous tubules. Conclusion: Results showed that using tamsulosin, possibly reduces the testosterone concentration through adrenergic axis system and in turn has destructive effects on proliferative activity of germ cells. Key words: Tamsulosin, Seminiferous tubules, Histopathology, Rat, Testis.