Ultrastructural changes induced by steroids and gonadotropins in cultured rat Sertoli cells

Testicular cells readily grew in cultures of seminiferous tubule fragments derived from adult rat testes. They formed confluent monolayers and continued to grow through four passages. The majority of cells had ultrastructural features characteristic of Sertoli cells. They exhibited large nuclei lacking heterochromatin, having nuclear membrane clefts, prominent nucleoli, significant amounts of agranular endoplasmic reticulum, large and numerous mitochondria, and lipid droplets. Cultured Sertoli cells responded to follicle-stimulating hormone (FSH), androgens, and dbcAMP by undergoing distinct morphological and ultrastructural changes. FSH induced parallel arrays of granular endoplasmic reticulum. Testosterone and dbcAMP resulted in the swelling of mitochondria, the formation of parallel cristae that stretched across the lumen, and the appearance of lipid droplets. Sertoli cells, cultured in a medium containing testosterone and FSH since their initiation, developed extensive agranular endoplasmic reticulum, strikingly large lipid droplets, and mitochondria that were characterized by either a dark matrix and vesicular cristae, or a light matrix and parallel cristae. These results indicate that Sertoli cells respond in vitro to hormones that are active in vivo, and support the suggestion that the Sertoli cell is a site of steroid synthesis in the mammalian testis.