Study on the macromolecular synthesis in aging mouse seminiferous tubules by light and electron microscopic radioautography.

Morphologic alternation and the changes of DNA, RNA and protein syntheses of the seminiferous tubules of aging mice were studied by light and electron microscopic radioautography. The morphology varied characteristically during the developmental periods. At embryonic and neonatal stages, the labelled myoid cells and Sertoli cells with 3H-thymidine were well observed, while at adult period, the labeling indices of both cells decreased to low levels. In contrast to this, the radioautograms showed that the gonocytes did not incorporate the labelled thymidine at embryonic day 19. As development proceeded to the 4th day after birth, the activity of DNA synthesis of gonocytes started. The labeling indices of spermatogonia reached the first peak at 3 weeks and were nearly constant thereafter. On the other hand, the activity of RNA synthesis of the cells in seminiferous tubules was not prosperous at embryonic day 19 and the neonatal stage. It was vigorous at adult and maintained a relatively high level at old period. The aging change of protein synthesis was detected in all kinds of the cells one hour after the 3H-leucine labeling. These results indicated that the old mice still kept adequate spermatogenesis. The Sertoli and myoid cells may play an important role in spermatogenesis in the whole life.