The purpose of this study was to test whether the lack of testicular growth found in suspended rats would affect
testosterone production in a way that might have consequences on
muscle atrophy and function studies. Body and testes weight, food consumption, and
testosterone levels in testes and plasma were measured at the beginning of the experiment and after 1, 3 or 8 weeks of
suspension. Suspended animals ate more but gained less weight than their pair-fed controls. Testes
testosterone concentration (microgram/g tissue) was increased at 3 and 8 weeks, but total tissue
testosterone (microgram/testes) was not. Up to 3 weeks of
suspension, tissue concentration was dependent on testes size and independent of treatment. Plasma
testosterone was increased only after 8 weeks of
suspension. At 8 weeks, plasma levels correlated with total testes
testosterone. Our results show that use of the Morey-Holton rat tail-suspension model up to 3 weeks did not induce
testosterone changes of consequence to a skeletal muscle study. For long term studies consideration should be given to possible hormonal effects as tissue and plasma
testosterone levels increase after 8 weeks of
suspension.