TESTES SIZE AND TESTOSTERONE LEVELS IN A MODEL FOR WEIGHTLESSNESS

The purpose of this study was to test whether the lack of testicular g rowth found in suspended rats would affect testosterone production in a way that might have consequences on muscle atrophy and function stud ies. 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 b ut gained less weight than their pair-fed controls. Testes testosteron e concentration (mu g/g tissue) was increased at 3 and 8 weeks, but to tal tissue testosterone (mu g/testes) was not. Up to 3 weeks of suspen sion, tissue concentration was dependent on testes size and independen t of treatment. Plasma testosterone was increased only after 8 weeks o f suspension. At 8 weeks, plasma levels correlated with total testes t estosterone. Our results show that use of the Morey-Holton rat tail-su spension model up to 3 weeks did not induce testosterone changes of co nsequence to a skeletal muscle study. For long term studies considerat ion should be given to possible hormonal effects as tissue and plasma testosterone levels increase after 8 weeks of suspension.