Association between intermediate-sized filaments and mitochondria in rat Leydig cells.

The cytoplasmic filamentous structures of the testis Leydig cells have been studied in the rat after double fixation with glutaraldehyde and osmium-potassium ferrocyanide. A good preservation of the cytoplasmic filaments was obtained and their abundance in the rat Leydig cells become apparent. Judging from their diameter (8-11 nm) and general morphology most of the filaments observed belong to the intermediate-sized type. The close association between filament bundles and mitochondria is described. Some images show cross-bridges between individual filaments and mitochondria and their attachment to the mitochondria outer membrane.