Growth hormone or insulin-like growth factor-I extends longevity of equine spermatozoa in vitro.

Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are both present in blood plasma and IGF-I has been measured in epididymal fluid and seminal plasma. This study was designed to investigate the direct effects of GH or IGF-I on the motility of mature equine spermatozoa in vitro. We compared the effects of one concentration (100 ng/ml) of recombinant bovine GH (rbGH) and recombinant human IGF-I (rhIGF-I) on motility and motion characteristics of equine spermatozoa over a 24 h period. Motility was maintained longer in spermatozoa treated with either rbGH or rhIGF-I during a 24 h period at room temperature (P < 0.05). Spermatozoa motion characteristics at time 0, 1, 2, 4, 6, 12 and 24 h for both rbGH and rhlGF-I were not significantly different from the respective controls. This study has shown that GH and IGF-I are effective in promoting the in vitro longevity of spermatozoa.