A morphological study of the epididymides of control and estradiol-treated prepubertal dogs.

Treatment of laboratory beagles with 400 micrograms of estradiol benzoate every fourth day from 5 to 20 wk of age severely alters the gross and microscopic morphology of the epididymis. Both stroma and epithelium are affected by estradiol treatment. The peritubular cells of treated animals appear to be fibroblasts separated by broad expanses of collagen, while the control peritubular cells resemble smooth muscle cells separated by small amounts of collagen. The single epithelial cell type present in the treated pup is low columnar and relatively undifferentiated in appearance. These cells appear to be synthetically active based on the accumulation of material within the lumen. The junctions of the epithelial cells of treated animals are occluding, but those of the control are not. The epithelium of control epididymides is composed of columnar principal cells in the caput epididymidis, and principal cells and basal cells in the pseudostratified epithelium of the corpus and cauda epididymidis. The epididymis of the intact, prepubertal dog is responsive to increased estrogen. The presence of estrogen and progesterone receptors (Jones and Connell, 1982) as well as androgen receptors (Younes et al., 1979) suggests that estrogens, progestins, and androgens all may play an essential role in the normal differentiation of the prepubertal epididymis. This is the first description of the ultrastructure of the epididymis of the 20-wk-old dog and the first description of the effect of chronic estrogen treatment on the ultrastructure of the epididymis of the intact prepubertal dog. We propose that the prepubertal dog epididymis is an excellent model system for the study of the hormonal control of epididymal differentiation and development.