Radioautographic study of the macromolecular synthesis of Leydig cells in aging mice testis

The studies on DNA, RNA and protein synthesis of Leydig cells in aging mice testis of several groups were carried out by light microscopic radioautography. The cells labelled with 3H-thymidine, 3H-uridine and 3H-leucine were observed in various aging groups. The labeling index with 3H-thymidine was low at embryonic and early postnatal stages. It increased slightly at 6 months, reached its peak at 9 months and maintained a relatively high level at a later period. The number of the silver grains labelled with 3H-uridine over the nuclei and cytoplasm were observed from embryonic day 19 and increased from 3 months onwards. From adult to old ages, the activity of 3H-uridine incorporation was maintained at a high level in the nuclei and a relatively low level in the cytoplasm. The aging change of 3H-leucine incorporation was found from this experiment. The labeling indices between embryonic and early postnatal stages showed no obvious differences while the number of the silver grains over both cytoplasm and nucleus increased from 6 months onwards and was maintained a high level until old age.