Influence of hypoxanthine concentrations on capacitation, acrosome reaction and In vitro fertilization in Ram Spermatozoa

The aim of the study was to evaluate the effect of hypoxanthine concentrations and incubation time on motility, hyperactivity (HA) and acrosome reaction (AR) in ram sperm in vitro. Semen samples (n= 40) were collected using artificial vagina from 3 mature Barki rams. Freshly ejaculated spermatozoa were pooled and subjected to swim up technique in modified sperm Tyrode's albumin lactate pyruvate (S-TALP) medium supplemented with different concentrations of hypoxanthine (5, 10, 15, 20 mg/ml). Motility, hyperactivity percentage and acrosomal status were recorded at 0, 1, 2, 3 and 4 h post-incubation. They were examined for ability to fertilize oocyte in vitro. The results showed that hypoxanthine concentrations and incubation time for 2 h did not significantly affect the motility. However, increase in incubation time for >2 h significantly (P<0.05) decreased the motility of spermatozoa as compared to control. Treatment of spermatozoa with 20 mg/ml hypoxanthine significant (P<0.05) increased in HA after 2 h of incubation compared to control (5.2±0.3 vs. 1.0± 0.1%). Significant (P<0.05) increase in total AR was associated to the increase in concentration of hypoxanthine with maximum at 20 mg/ml at 3h of incubation (82.0±2.2%). The fertilization rate of oocytes treated with 20 mg/ml hypoxanthine was higher as compared with control (42.8 vs. 26.0%). In conclusion, treatment of ram spermatozoa with 20 mg/ml hypoxanthine for 2 to 3 h was considered the best concentration for in vitro fertilization in sheep.