4. Discussion: The present study has collectively evaluated the presence of CatSper channels and their characteristics in bull sperm, thus providing a novel insight into the cellular mechanisms that induce hyperactivation and rheotaxis in bull sperm. The main finding of this study was that the known calcium channel inhibitor Mibefradil produced an inhibitory effect on bovine sperm hyperactivation. This effect occurred as a delayed induction of hyperactivation. Furthermore, it was found that Mibefradil produced an inhibitory effect on sperm progression through a microfluidic device in comparison to the caffeine controls. This finding in conjunction with the observed stimulatory effects of high extracellular pH, NH4Cl and caffeine indicates that …show more content…
al, 2014) have investigated the effect of rheotaxis on bull sperm navigation through a microfludic device. Tung et. al, (2014) reported rheotactic behaviour of bull sperm in grooved microchannels mimicking the cervix walls in the female reproductive system. It was found that these grooves helped sperm cells to migrate against fluid flow. Furthermore, the speed of sperm cells swimming against the flow was found to decrease with an increase in the flow rate inside the microchannel. In this current study, rheotaxis was also found to play a role in sperm progression though the microchannel. Using the optimum flow rate for the device it was found that untreated sperm progressed though the device and exhibited positive rheotaxis. This indicates that rheotaxis could play an essential role in the long distance navigation of bull sperm through the female reproductive tract to the oocyte (Miki et. al, 2013). This finding is substantiated by a similar finding in studies by Kantsler et. al …show more content…
al, 2014). El Sherry et. al (2014) concludes that flow velocity plays an important role in regulating sperm rheotactic behaviour. El Sherry et. al (2014) suggests that mechanical effects may exist through mechanosensing ion channels (MSCs) due to fluid shear stress increasing on the membrane of sperm head with an increase in the liquid velocity. MSCs are stretch activated channels that respond to mechanical stress on the cell membrane by allowing certain ions to enter the cell (Sachs, 2010). When a sperm swims against the flow, it experiences an increase in liquid pressure at its most upstream tip where the liquid is brought to a halt. This pressure rise increases with the flow velocity. In addition, the fluid drag / shear stress on sperm head also increases with flow velocity (El-Sherry et. al, 2014; Kantsler et. al,