Differential expression of glucose transporter GLUT8 during mouse spermatogenesis.

GLUT8 is a facilitative glucose transporter expressed at high levels in the testis. In this study, we analyzed the GLUT8 expression in mouse testis during spermatogenesis by RT-PCR, Western blot and immunohistochemistry methods. Our results show that GLUT8 expression is limited to spermatids and spermatozoa in the testis. Expression begins when round spermatids are formed at postnatal day 24. The expression persists throughout spermiogenesis, and it is also detected in spermatozoa, but it is absent in more immature germ cells, Sertoli cells and interstitial tissue. GLUT8 immunoreactivity is always restricted to the acrosomic system in a manner that matches the acrosome system formation. The GLUT8 expression is mainly associated with the acrosomic membrane in the acrosome, although significant immunoreactivity is also found inside the acrosomic lumen. The specific GLUT8 location suggests that this transporter plays a pivotal role in the fuel supply of spermatozoa, and in the traffic of sugars during the capacitation and fertilization processes.