Species: Hamster, Syrian Golden Strain/breeder: Han: AURA (Fraunhofer ITEM Hannover, Germany) Sex: Male + Female Age: 8-10 weeks Study type: Two 3 months studies (A+B), oral Treatment: Control Animal status: Scheduled kill Clinical findings: No clinical findings Organ(s): Testes, vagina Gross finding(s): Study A: no findings (slide 6a+6c); study B: diminished in size (slide 6b+6d) Staining: H&E Literature: -

Fig. 1 (6a) (100k) Fig. 2 (6b) (107k) Fig. 3 (6c) (79k) Fig. 4 (6d) (95k)

Abstract

A. Heuser, J. Kemkowski, and G. Bode

ALTANA Pharma AG, Institute of Pathology and Toxicology, Hamburg, Germany

Key words: Hamster, light period, reproductive organs

Purpose: To investigate the influence of the duration of light period on reproductive organs in male and female Syrian golden hamsters.

Methods: Two groups of male and female Syrian golden hamster (HAN:AURA) were exposed to a light regimen with either equal light/dark cycles (LD 12/12 hours) or a prolonged light period (LD16/8 hours) for 3 months. Male and female reproductive organs were examined histologically.

Results and Conclusions: In LD 12/12 males, testes showed varying degrees of arrested spermiogenesis. Secretory activity in prostate and seminal vesicles was reduced. Histology of LD 16/8 males indicated normally functioning gonads. In LD16/8 females the vaginal morphology revealed a normal distribution of cyclic stages whereas the majority of LD 12/12 females were in an inactive stage resembling metestrus. In the ovaries of LD 12/12 females, interstitial tissue was increased.

Photoperiod is a critical regulator of reproduction in hamsters. Shortened light periods can induce pseudo-hibernation with regression of male and female gonads. By adjusting light/dark cycle these changes are fully reversible. It is important to be aware of photoperiod induced changes in hamster gonads to avoid misinterpretation as treatment related degenerative or atrophic changes.