Testicular
steroid content and Leydig cell steroidogenesis in vitro were investigated in rams on Days 28 and 58 after Trypanosoma congolense
infection and were compared with those of rams in which testicular temperature had been raised artificially by insulation of the scrotum for 58 d. Testicular
testosterone content increased significantly on Day 28 after
infection but was lower than that of controls on Day 58 while it increased in scrotal-insulated rams compared with that of controls by Day 58. Testicular
progesterone was undetectable in the control and trypanosome-infected groups throughout the experiment, but it increased in the insulated rams by day 58. Basal (unstimulated) Leydig cell
testosterone production in the infected rams was similar to that of control rams on Day 28 but was significantly lower on Day 58. Stimulation of Leydig cell
testosterone production with hCG or
22R-hydroxycholesterol (22ROHC) significantly reduced in infected rams at both 28 and 58 d after
infection as well as in scrotal-insulated rams on Day 58. It is concluded that the increase in testicular
testosterone content in the infected and scrotal-insulated rams on Days 28 and 58, respectively, was induced by elevation of testicular temperature by trypanosome
infection, perhaps through an effect on testicular blood flow. Reduced
testosterone production by Leydig cells from infected and scrotal-insulated rams in response to hCG and 22ROHC suggests that trypanosome-induced
pyrexia might be involved in reducing Leydig cell steroidogenesis and subsequent plasma
testosterone levels, possibly by affecting
enzymes involved in
steroid biosynthesis.