Localization of specific glycoproteins secreted by the rabbit and hamster epididymis.

Abstract

To investigate the origin and fate of a number of specific epididymal proteins, the luminal contents from the cauda epididymides of sexually mature New Zealand White rabbits and Syrian hamsters were collected by retrograde perfusion. Epididymal fluid, separated from spermatozoa by centrifugation over a 10% Ficoll solution, was then subjected to isoelectric focussing on polyacrylamide flat bed gels. Three epididymal-specific proteins from the rabbit, pI 3.45, 4.15 and 4.65 and two from the hamster, pI 3.40 and 4.15 were identified as glycoproteins by their low isoelectric point and their affinity for concanavalin A. These fractions were isolated and implanted s.c. in guinea pigs and rabbits, respectively, to produce monospecific antisera as verified by immunodiffusion and immunoelectrophoresis. Localization of glycoprotein antigen within the epididymis was performed on longitudinal sections of snap-frozen epididymis using the unlabeled antibody enzyme method. Both rabbit and hamster glycoproteins were secreted mainly by epididymal epithelial cells in the caput and proximal corpus region. However, the initial segments and testis were devoid of antigen. Differences were also apparent in the staining pattern of individual glycoproteins. In the rabbit, glycoproteins were first associated with spermatozoa in the distal caput and proximal corpus epididymidis while glycoproteins in the hamster epididymis were first associated with spermatozoa in the proximal caput region. Reaction product to glycoproteins in the cauda epididymidis of both species was present on spermatozoa and at the adluminal border of epithelial cells. The significance of these results with regard to changes in the surface composition of the sperm plasmalemma during maturation is discussed.