Photoperiodic modulation of thyroid hormone receptor (TR-α), deiodinase-2 (Dio-2) and glucose transporters (GLUT 1 and GLUT 4) expression in testis of adult golden hamster, Mesocricetus auratus

Abstract

Phenomenon of seasonal reproduction is being regulated by changes in day length or photoperiod. The molecular mechanism underlying the event of photoperiodic regulation of testis and thyroid functions along with glucose uptake transporters has never been reported for golden hamster, M. auratus. The present study was performed to investigate the effect of photoperiod on the expression of key thyroid hormone receptor (TR-α), deiodinase-2 (Dio-2) and glucose uptake transporters (GLUT-1 & GLUT-4) in testicular germ cell and Leydig cells, and its correlation with the testicular androgen receptor (AR), germ cell proliferation factor (PCNA) and cell survival factor (Bcl-2) in testis of adult golden hamster, Mesocricetus auratus. Hamsters were exposed to different photoperiodic regimes i.e. critical photoperiod (CP), short day (SD) and long day (LD) for 10weeks. LD induces upregulation of thyroidal and gonadal activity as evident by active thyroid gland and testicular histoarchitecture, peripheral total thyroid (tT3, tT4) and testosterone hormone profiles when compared with SD exposed hamsters. Further, LD increased the expression of testicular TR-α, Dio-2, GLUT-1, GLUT-4 along with testicular AR and glucose content thereby enhancing germ cell proliferation and survival as reflected by increased PCNA and Bcl-2 expression when compared to SD exposed hamsters. Thus, it can be suggested that testicular thyroid hormone status is being regulated by photoperiod and is possibly involved in seasonal adaptation to reproductive phenomenon of golden hamster.