Epithelial structure of the rat cauda epididymidis after luminal perfusion.

When solutions containing high concentrations of sodium ions (c. 140 mM) were perfused for up to 6 h through the lumen of the cauda epididymidis of the anaesthetised rat, distended spaces were consistently seen between the epithelial cells, water resorption was measurable, and clear cells lacked large clear apical vacuoles. Lowering the sodium ion concentration decreased water resorption, and distended intercellular channels were absent. Under these conditions clear cells had abnormally large or numerous pale staining vacuoles. When physiological concentrations of sodium (20 mM) and potassium (50 mM) ions were perfused, a more normal epithelium was present; intercellular channels were absent, and water was either resorbed or secreted at low rates. Clear cells appeared normal initially, but had abnormal appearance after longer periods of perfusion.