Principal cells of the vas deferens are involved in water transport and steroid synthesis in the adult rat

Principal cells show marked structural differences in the proximal, middle, and distal regions of the vas deferens, reflective of diverse functional a ctivities. In the present study, we performed electron microscopy to examin e the structural features of principal cells using glutaraldehyde-fixed, Ep on-embedded material, while functional parameters were examined using light microscopic immunocytochemistry on Bouin-fixed, paraffin-embedded material . in the proximal region, the cuboidal principal cells resembled those of t he cauda epididymidis, but few dear cells and occasional narrow cells were present. in the middle region, principal cells often contained blebs of the ir apical cytoplasm containing vesicular and tubular profiles. These blebs extended far from the cell surface and appeared to be liberated into the lu men, suggesting an apocrine type of secretion. In the distal region, dilate d intercellular spaces containing numerous membranous profiles of different shapes and sizes were noted between adjacent principal cells and overlying basal cells. The use of an anti-aquaporin-1 antibody revealed an intense r eaction over the endothelial cells of numerous vascular channels in the lam ina propria. Taken together, these observations suggested water transport f rom the lumen of the vas deferens via the dilated spaces to underlying vasc ular channels, the function of which may be to concentrate sperm. The infra nuclear cytoplasm of principal cells of this region showed whorls of smooth endoplasmic reticulum (sER). Large intracytoplasmic cavities were found wi thin the sER aggregates, and these contained membranous profiles that appea red to peel off from the surrounding sER elements. Various images of such c avities closely juxtaposed to the lateral plasma membrane suggested that th e membranous profiles of the intercellular spaces were derived from them. U se of anti-3 beta-hydroxysteroid dehydrogenase antibody revealed an intense reaction over principal cells of the vas deferens, as well as over the ble bs in the lumen of the vas deferens, which is indicative of the steroid syn thesis performed by these cells. The release of sER membranous profiles int o the dilated spaces and the presence of blebs in the lumen may represent a means of transporting steroids that are destined for different sites out o f the principal cells. Steroids in the blebs would be ultimately destined f or utilization by luminal sperm, while those steroids in the dilated spaces are designed for utilization by muscle layers of the lamina propria. In su mmary, principal cells of the vas deferens appear to be involved in synthes is and secretion of steroids and in eliminating water from the lumen of the vas deferens.