In vitro autoradiographic studies of DNA synthesis in human testis with spermatogenic arrest.

The uptake of 3 H‐thymidine by spermatogonia and resting spermatocytes was studied by autoradiography in human testis biopsies incubated in vitro from four groups of subjects: normal, prepuberal (hypogonadotropic hypogonadism), with spermatocytic arrest and with spermatidic arrest. In the prepuberal group there was a very low DNA synthesis rate. In the spermatidic arrest group the number of DNA synthesizing cells was higher than that of the normal control group while in the spermatocytic arrest group it was lower. These results indicate a possible different pathogenesis for the two forms of spermatogenic arrest. In the spermatocytic arrest there is a primary deficiency of germ cells synthesizing DNA, while in the spermatidic arrest, synthesis is active and the arrest is probably due to an enzymatic (?) metabolic block.