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

Abstract

Aim: 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. Methods: 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). Results: Progressive motility and the induction rate of capacitation and acrosome reaction were increased ( P < 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 ( P < 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 ( P < 0.05) in spermatozoa incubated with relaxin or IGF‐I alone or in combination compared with the control. Conclusion: Thus, supplementation of relaxin alone or combined with IGF‐I into the medium possibly plays a beneficial role in porcine spermatozoal prefertilization events in vitro . (Reprod Med Biol 2008; 7 : 29–36)