The effect of hyperthermia on the mouse testis.

The response of different stages of spermatogenesis to heat have been assessed by scoring the cell types in testis tubules at 14, 28 and 35 days after treatment. Deficiencies in spermatids at these times can be related back to the stage that the precursor would have been in 14 and 28 days earlier. On the 35th day the number of repopulated tubules was counted. The testes of CBA mice were heated using a radiofrequency equipment and controlled by a thermocouple in the other testis. Great difficulty was experienced in achieving a uniform temperature of 43 degrees C for a period of 30 minutes. The testes can be grouped into 2 categories: those with an appropriate heat profile and those which were overheated. The data showed that the weight of the testis at 14 days was only 65% of control and had slightly increased by 28 days to 88%. The number of sperm heads and late spermatids decreased to 33% at 14 days, but had increased to 88% by day 28. On the 35th day after heating to 43 degrees C cell depletion and shrinking of the tubules occurred. Sixty-four percent of examined tubules only had normal appearance and were repopulated. This shows that the temperature of 43 degrees C impairs the stem cells and it can be a warning to clinicians who think of applying hyperthermia for treatment of human tumors located in the testis area.