Does exercise affect female hamster gonadotropins by reducing estradiol negative feedback?

Area of Science:

• Reproductive Endocrinology
• Animal Physiology
• Exercise Science

Background:

• Exercise impacts reproductive function differently across species.
• Short-day photoperiod (SDP) inhibits hamster reproduction by increasing hypothalamo-pituitary-gonadal axis (HPGA) sensitivity to gonadal steroid negative feedback.
• Understanding exercise's role in reproductive regulation is crucial.

Purpose of the Study:

• To investigate if exercise facilitates reproduction in female hamsters by modulating the HPGA's sensitivity to estradiol negative feedback (ENF).
• To determine the influence of estradiol (E2) on basal luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations in exercising versus sedentary hamsters under different photoperiods.

Main Methods:

• Female hamsters were maintained under long-day (LDP) or short-day photoperiods (SDP).
• Ovariectomized (OVX) hamsters were either exercised or kept sedentary, with some receiving estradiol (E2) replacement.
• Serum LH and FSH concentrations were measured to assess HPGA activity.

Main Results:

• Under LDP, exercise had no effect or reduced LH/FSH in OVX hamsters, but increased LH with E2 replacement.
• Under SDP, exercising OVX hamsters showed significantly higher LH and FSH levels than sedentary controls, regardless of E2 treatment.
• Exercise effects on gonadotropin secretion were dependent on the level of estradiol negative feedback.

Conclusions:

• Exercise's impact on basal gonadotropin secretion in female hamsters is contingent upon the prevailing estradiol negative feedback (ENF).
• Exercise stimulates gonadotropin secretion when ENF is high (SDP and/or E2 treatment), possibly by reducing HPGA sensitivity to steroid feedback.
• This contrasts with exercise's inhibitory reproductive effects in women and rats, highlighting species-specific responses.