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This Article Full Text Full Text (PDF) All Versions of this Article: 293/3/R1368    most recent 00106.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Scherbarth, F. Articles by Steinlechner, S. Search for Related Content PubMed PubMed Citation Articles by Scherbarth, F. Articles by Steinlechner, S.

ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Wheel running affects seasonal acclimatization of physiological and morphological traits in the Djungarian hamster (Phodopus sungorus)

¹Institute of Zoology, University of Veterinary Medicine Hannover, Hannover, Germany; ²Faculty of Biology, Department of Animal Physiology, Philipps-University Marburg, Marburg, Germany; and ³Department of Endocrinology, Christie Hospital, Manchester, United Kingdom

Submitted 13 February 2007 ; accepted in final form 22 June 2007

Wheel running was previously shown to influence body mass and torpor in short-day-acclimatized Djungarian hamsters (Phodopus sungorus). To determine whether the exercise-induced effect on body mass depends on the annual phase, hamsters were exposed to the natural change in photoperiod and given access to a running wheel (RW), either before, in the middle of, or at the end of the descending body mass trajectory during seasonal acclimatization. Due to wheel running, the seasonal weight cycle was prevented or aborted by abruptly rising body mass, resulting in a weight appropriate for summer, despite exposure to short days. Torpor was inhibited, and testicular recrudescence was advanced, compared with controls. In contrast, the change into winter fur remained unaltered. Analysis of body composition and plasma leptin revealed a low body fat mass in RW hamsters, not only in winter but also in summer, suggesting a lack of seasonal adiposity. Chronic leptin infusion in winter only decreased body mass in RW individuals, although their relative body fat mass probably was even lower than in sedentary hamsters. A constantly low body fat mass is conceivably reflecting an exercise-dependent change in metabolism, consistent with increased bone mineral content and density in RW hamsters. Additionally, bone area was increased, again supported by elongated vertebral columns. Together, the results show a striking effect of wheel running on body composition and the seasonal pattern of body mass, and they suggest that the photoperiodic regulation of body mass is regulated differently than the reproductive and pelage responses.

body composition; torpor; testicular recrudescence; leptin