Morphological analysis of endocytosis in efferent ductules of estrogen receptor-alpha knockout male mouse.

Lack of estrogen receptor (ER) results in fluid accumulation and dilation of the efferent ductules, suggesting that the role of estrogen and ER in the male reproductive tract is related to fluid reabsorption in the ductules. In the present study, endocytosis of the nonciliated cells of the efferent ductules was compared morphologically between wild type (WT) and estrogen receptor-alpha knockout (alpha ERKO) male mice. The epithelial cells lining the WT efferent ductules were tall columnar in shape, whereas those of the alpha ERKO were low columnar. Immunocytochemically, the nonciliated cells of both genotypes showed positive reactions of sulfated glycoprotein-2, but the reaction products were reduced in amount in the alpha ERKO. Electron microscopy revealed that the nonciliated cells of the WT had numerous organelles for endocytosis such as coated pits and vesicles, tubules, endosomes, multivesicular bodies and lysosomes in the apical cytoplasm. These organelles were less developed in the nonciliated cells of the alpha ERKO. Morphometric analysis indicated that there was a significant reduction in area of endocytotic apparatus in the nonciliated cells of the alpha ERKO compared with that of the WT. A tracer study using gold particles demonstrated that the nonciliated cells of both WT and alpha ERKO efferent ductules were capable of taking up luminal contents. These results suggest that reabsorption of the luminal contents via endocytosis takes place in the efferent ductules but is greatly reduced in amount in the absence of ER alpha.