Effects of aging and oviductal hormones on testes, epididymides, and sperm of hamster

PURPOSE: Aging is a major cause of decreased fertility. Using hamster, we examined the effects of aging on testes, epididymides, and sperm. Additionally, we examined whether progesterone (P(4)), melatonin (Mel) and 5‐hydroxytryptamine (5‐HT) mitigated effects of aging on sperm. METHODS: Young (10–16 weeks), Adult (5–7 months), Aged (13–15 months), and Old (19–22 months) hamsters were used. Weights of bodies, testes, and epididymides were measured. Testes and epididymides were studied by histological microscopy. Sera were obtained to determine testosterone concentrations. Sperm were analyzed by video‐microscopy. RESULTS: By aging, body weights increased but weights of testes and epididymides decreased. Most hamsters were normozoospermia, although several old hamsters were azoospermia. In testes and epididymides, desquamation and structures resembling residual bodies (SRRBs) were observed. Although desquamation was not always related to aging, SRRBs occurred by aging. Testosterone concentrations were not changed in normozoospermic hamsters, but it was significantly reduced in old azoospermic hamster. Aging significantly reduced sperm ability to exhibit hyperactivation. Additionally, aging significantly increased the straight‐line velocity (VSL). P(4), Mel, and 5‐HT lessened the reduction in sperm hyperactivation and the increasing of VSL. CONCLUSION: Aging reduces qualities of testes, epididymides, and sperm, and P(4), Mel, and 5‐HT recover reduced quality of sperm.