Background: A previous study revealed that exposure of rats to microgr
avity for 14 d on Cosmos 2044 reduced production of testosterone by >8
0%, although spermatogenesis remained essentially normal. Methods: To
ascertain if testicular function was altered in hypergravity, 60-d-old
rats were randomly assigned to 2 groups (10 per group) and subjected
to 14 d of centrifugation to expose them to a total of 2G, or held at
unit gravity in similar cages without centrifugation (control). Result
s: After 14 d, body weight of 2G rats was essentially unchanged, where
as that of control rats had increased; 310 vs. 377 g (p < 0.05). Teste
s weight, production and secretion of testosterone, diameters of semin
iferous tubules and their lumina, data from subjective evaluation of s
permatogenesis, and counts of homogenization-resistant spermatids ail
were similar for 2G and control rats. Conclusion: It was concluded tha
t exposure of male rats to 2G for 14 d had no major effect on testicul
ar function whereas, based on earlier studies, exposure to microgravit
y (<10(-3) x gravity) for 11-14 d suppressed production of testosteron
e by Leydig cells and reduced concentrations of anabolic steroids avai
lable to peripheral tissues.