The fine structure of testicular interstitial cells in the mouse. A comparison after conventional double fixation versus rapid freezing followed by freeze substitution.

The interstitial cells in the testis of the mouse have been studied both after conventional double fixation with glutaraldehyde followed by osmium tetroxide and after rapid freezing and cryosubstitution with osmium tetroxide-acetone by light, scanning and transmission electron microscopy. Differences have been found especially concerning the preservation of lipids and the appearance of mitochondria. Varying proportions and different aspects of rough and smooth endoplasmic reticulum were observed corresponding after both preparation methods thus confirming their real existence. Numerous specific contacts are found between macrophages and Leydig cells, indicating a functional interdependence between these two cell types. Though structural preservation is superior after freeze substitution in the outermost zone, artifacts caused by the initial impact, by ice crystal formation, and during substitution must be considered.