Leydig cell function and morphology in the rat testis after exposure to heat.

Leydig cell function, as judged from testosterone concentrations in plasma and in testicular tissue after LH stimulation, was tested in adult rat testes 4 days after brief exposure of the scrotum to 33 degrees and 43 degrees C, respectively. There was no significant difference in basal plasma testosterone concentrations between the two groups of rats but the response to LH stimulation was significantly depressed in rats exposed to 43 decrees C. Morphological examination of the Leydig cells showed an accumulation of lipid droplets in the cytoplasm of the testes exposed to 43 degrees C, indicating a disturbed steroidogenesis. The spermatogenetic arrest seen after heat treatment of the rat testis is discussed in relation to the present finding of impaired Leydig cell function.