ULTRASTRUCTURAL AND AUTORADIOGRAPHIC STUDIES ON DNA-SYNTHESIS IN LEYDIG-CELLS OF AGING MOUSE TESTIS

A morphological observation and a radioautographic study were carried out to detect the ultrastructure and aging changes of DNA synthesis of the Leydig cells, whose structure has been observed and the area of t he lipid droplets in the cytoplasm calculated. The observation by elec tron microscopy showed that Leydig cells contained abundant mitochondr ia and endoplasmic reticulum and that the area of the lipids in the cy toplasm changed with aging. Only little lipid droplets were found in e mbryonic and early postnatal stages, but they increased from postnatal two weeks onwards and no significant differences were found from 9 mo nths to 21 months. The DNA synthesis in these cells was not vigorous a t embryonic day 19, explored by light microscopic radioautography 1 hr . following a single injection of H-3-thymidine. The labeling index in creased slightly before six months of age and reached its peak at 9 mo nths. There was no significant difference found in the number of label led cells from that time on. A relatively high level was maintained at adult and senescent periods. Our results demonstrate that the generat ion of the Leydig cells contained plentiful lipid droplets was vigorou s at adult and senescence.