Sex Steroid Regulation of Daily Physical Activity Levels in Male Balb/cJ Mice

Abstract

Testosterone and 17β-estradiol have been shown to increase physical activity in rodents. Measurement of sex steroid-regulated wheel running activity has commonly been quantified by measuring the distance, duration, and speed of activity over a 24hr period. PURPOSE: To evaluate the effects of testosterone and 17β-estradiol on wheel running distance, duration, and speed in male Balb/cJ mice. METHODS: Male (experimental=5, sham=5) Balb/cJ mice were provided access to running wheels equipped with cycling computers for seven days to track distance (km·day-1) and duration (min) of wheel running (1) under normal physiological conditions, (2) after orchidectomy (ORCH), (3) after ORCH and supplementation with testosterone, and (4) after ORCH and supplementation with 17β-estradiol. Testosterone and 17β-estradiol were supplemented via silastic implants. The silastic implants were prepared in 10 mm sections and contained 2.6 mm3 of powder steroid. Speed (m·min-1) data were calculated from distance and duration. Additionally, body mass (g), food consumption (g), % body fat, and bone mineral density (g·(cm2)-1) were measured. Data were analyzed via two-way ANOVAs with Tukey's HSD post-hoc tests. RESULTS: Distance and duration were significantly decreased after orchidectomies alone and during supplementation with 17β-estradiol compared to sham animals (p<0.05). Wheel running activity was recovered after testosterone supplementation (p>0.05). Running speed remained constant between experimental and sham animals across all conditions. Body mass, food consumption, % body fat, and bone mineral density were not different between the experimental and sham groups. CONCLUSION:In vivo testosterone supplementation in male mice increased daily physical activity levels and supported previous literature. Our data suggest that sex steroid concentration can influence daily activity levels in male mice.