Ultrastructural study of epithelial cells and basement membrane. Differentiation of the rat epididymis after prenatal irradiation.

The effects of prenatal irradiation on the testis are well documented, but less is known about its effects on epididymal differentiation. Pregnant rats were irradiated on the 18th day of gestation. The increase in microfilaments and lipid inclusions in the epithelial cells, in favor of a direct radiation effect, is maximal at birth and disappears thereafter. Narrow cells and clear cells show a normal differentiation pattern. On the other hand, the principal cell maturation is largely altered. The synthesis capacities are decreased based on a reduction in the size of the Golgi apparatus and the smooth endoplasmic reticulum. The aspects of invaginations of the apical plasmalemma, coated vesicles and multivesicular bodies are not modified, suggesting normal absorption functions. The epithelial basement membranes become irregular and thicker than normal, enfolding the basal part of the epithelial cells. The basement membrane proteoglycans, demonstrated by the cationic marker polyethyleneimine, are irregularly distributed in contrast to the normal pattern. These modifications of the principal cells and the basement membrane are more prominent in the proximal epididymis. This suggests a differential maturation dependence of the epithelial cells on the luminal factors, normally secreted by the testis, and likely disturbed by prenatal irradiation which leads to germ cell degeneration, and then to a new balance in the seminiferous epithelium.