Angiotensin-II induced nitric oxide production during buffalo sperm capacitation and acrosome reaction

The present study was designed to see the effects of Angiotensin-II (Ang-II) on buffalo sperm capacitation, acrosome reaction (AR), and its relation to nitric oxide (NO) production. The extent of capacitation or AR was determined by dual staining while the NO production was determined by spectrophotometry. The results thus obtained revealed that Ang-II induced capacitation in a concentration and time dependent manner and 200 nM Ang-II was found to be optimal for capacitation as it was comparable to heparin treatment (50.7 ± 2.45% vs. 51.66 ± 2.33%). In capacitated cells the extent of AR induced by Ang-II was significantly higher than the untreated control (48.13 ± 2.31% vs. 22.16 ± 2.11%) and comparable to lysophosphatidyl Choline (LPC) treatment (51.56 ± 1.94%). The NO production during Ang-II induced capacitation and AR was gradual and time dependent. These levels were significantly higher when compared to control (3.65 ± 0.53 nmoles/108 cells vs. 9.12 ± 0.30 nmoles/108 cells). All the actions of Ang-II were inhibited in the presence of Losartan but not PD123319, indicating the role of AT1 receptors in these actions. Further the NO production was also significantly inhibited in the presence of neomycin and trifluoperazine pointing towards the role of phosphoinositide pathway in this process. In conclusion, Ang-II has a concentration and time dependent effect on buffalo sperm capacitation and AR, mediated via the AT1 receptors. Its effect on NO production may be indirect involving the phosphoinositide pathway.