Effects of relaxin and IGF-I on capacitation, acrosome reaction, cholesterol efflux and utilization of labeled and unlabeled glucose in porcine spermatozoa.

Relaxin and insulin-like growth factor (IGF)-I have pronounced effects on the male and female reproductive tracts. The aim of this study was to investigate the effects of relaxin and IGF-I on the motility, capacitation, acrosome reaction, cholesterol efflux and utilization of glucose in porcine spermatozoa. Swim-up separated spermatozoa that had been washed twice were incubated at 37°C for 1 or 4 h in modified Tyrode's albumin lactate pyruvate (mTALP) medium supplemented without (control) or with relaxin (20 ng/mL) or IGF-I (20 ng/mL) or both (10 + 10 ng/mL). Progressive motility and the induction rate of capacitation and acrosome reaction were increased ( 0.05) by relaxin and IGF-I alone or in combination, especially after 4 h of incubation. Relaxin alone or combined with IGF-I enhanced ( < 0.05) the cholesterol efflux after 4 h, whereas IGF-I alone did not show any significant effect on the cholesterol efflux compared with the control at any time point. The utilization rates of labeled and unlabeled glucose increased ( 0.05) in spermatozoa incubated with relaxin or IGF-I alone or in combination compared with the control. Thus, supplementation of relaxin alone or combined with IGF-I into the medium possibly plays a beneficial role in porcine spermatozoal prefertilization events . (Reprod Med Biol 2008; : 29-36).