Development of the Sertoli cell in the fetal mouse

Ultrastructural changes were observed in the organelles of the Sertoli cells of the mouse during fetal development. At day 13 of development, the cells contained predominantly rough-surfaced tubular endoplasmic reticulum, numerous polysomes and multiple Golgi complexes. Day 14 appears to be a transition stage with equal amounts of tubular and vesicular endoplasmic reticulum. But by day 15 and through day 16, only vesicular endoplasmic reticulum, some profiles of which exhibited oligogranularity, annulate lamellae and lipid droplets were observed. This appearance suggests steroid synthesis. Days 17-20 were characterized by a gradual decrease in vesicular elements with a concomitant increase in rough endoplasmic reticulum and polysomes.