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

Quantification of fecal estradiol and progesterone metabolites in Syrian hamsters (Mesocricetus auratus)

Alternative methods to the utilization of laboratory animal blood and its by-products are particularly attractive, especially regarding hamsters due to their small size and difficulties in obtaining serial blood samples. Steroid hormone metabolite quantification in feces, widely used in studies of free-ranging or intractable animals, is a non-invasive, non-stressor, economical, and animal saving technique which allows longitudinal studies by permitting frequent sampling of the same individual. The present study was undertaken to determine the suitability of this method for laboratory animals. Estradiol and progesterone metabolites were quantified by radioimmunoassay in feces of intact, sexually mature female Syrian hamsters during the estrous cycle (control) and in feces of superovulated females. Metabolites were extracted by fecal dilution in ethanol and quantified by solid phase radioimmunoassay. Median estrogen and progesterone concentrations were 9.703 and 180.74 ng/g feces in the control group, respectively. Peaks of estrogen (22.44 +/- 4.54 ng/g feces) and progesterone (655.95 +/- 129.93 ng/g feces) mean fecal concentrations respectively occurred 12 h before and immediately after ovulation, which is easily detected in this species by observation of a characteristic vaginal postovulatory discharge. Median estrogen and progesterone concentrations (28.159 and 586.57 ng/g feces, respectively) were significantly higher in superovulated animal feces (P < 0.0001). The present study demonstrated that it is possible to monitor ovarian activity in Syrian hamsters non-invasively by measuring fecal estradiol and progesterone metabolites. This technique appears to be a quite encouraging method for the development of new endocrinologic studies on laboratory animals.

Characterization of serum dehydroepiandrosterone secretion in golden hamsters

Dehydroepiandrosterone (DHEA) is an adrenal androgen whose function is poorly understood. Although DHEA and DHEA sulfate (DHEAS) are secreted in relatively high quantities by the human adrenal, the laboratory rat secretes very little, thus hindering experimental studies of the hormone. In this paper, we measured the changes in serum DHEA and DHEAS under various physiological conditions in golden hamsters. Evening serum DHEAS fell from 6.30 +/- 0.78 microg/dl (mean +/- SE) before surgery to 3.03 +/- 0.23 microg/dl 12 days after bilateral adrenalectomy. Hamsters had higher levels of DHEA and DHEAS in the evening than in the morning, but removal of the gonads did not consistently decrease serum DHEA or DHEAS in males or females. Evening levels of DHEA and DHEAS reached a peak around 7 weeks of age and then gradually decreased to about one-third of these levels by one year of age. These results suggest that DHEA and DHEAS are secreted at least in part from the hamster adrenal, that they do not originate from the gonads, and that there is a daily rhythm with peak levels at a time of day just preceding the active phase. In addition, the levels of these hormones decrease with aging.