Purification, Radioimmunoassay, and Immunohistochemical Localization of a Glycoprotein Produced by the Rat Epididymis

Abstract

During the epididymal transit of spermatozoa, their membranes become coated with glycoproteins, which may play an important role in fertilization. One of these glycoproteins has been purified from rat epididymides. It has a molecular weight of 37,500 daltons, and an isolectric point of 4.7. By use of a specific radioimmunoassay, it was shown that this glycoprotein is detected only in the epididymis and the deferent duct. It is detectable at 20 days of age and increases progressively to reach a plateau between 3 and 4 months of age (15.7 ± 0.9 μg/mg protein, mean ± SD, n = 20). It disappears after castration and reappears after testosterone treatment. Estrogens have no effect on its production. lmmunohistochemical studies show that it is produced by epithelial cells of the caput (distal to the initial segment) and of the corpus epididymidis and suggest that its resorption takes place in the cauda epididymidis and the deferent duct.