Quantitative studies of cytological damage in mouse testis produced by exposure to heat.

Damage in gonadal cells produced by exposure of the hindquarters of conscious male mice to water at temperatures up to 43 degrees C was studied by measuring the percentage of testicular cells which do not exclude trypan blue 4 h after exposure, sperm count up to ten wk later, and the percentage of morphologically abnormal sperm up to ten wk later. It was found that the percentage of cells stained with trypan blue was significantly increased by exposure for 0.5 h at 41 degrees C or 2 h at 37 degrees C. Sperm count and the percentage of abnormal sperm were affected by 0.5 h at 43 degrees C or 2 h at 40 degrees, but not by lower temperatures. Since there is a high incidence of abnormal sperm after some heat treatments, the use of this assay for mutagen screening should be approached with caution.