Rabbit Epididymal Secretory Proteins. I. Characterization and Hormonal Regulation1

Abstract

Analyses of samples of luminal fluid from the rete testis, distal efferent ducts, and epididymal regions 2-5 and 8 revealed that 91% of the fluid leaving the testis is reabsorbed by the efferent ducts, 79% of the remainder is reabsorbed proximal to epididymal regions 4 and 5, and there is a net secretion of fluid into the duct caudally. There is a net reabsorption by the efferent ducts of 73% of the protein leaving the testis and then a net secretion along the epididymis. SDS-PAGE of the luminal fluids indicated that four new protein bands that were not present in blood appeared in the efferent ducts, 5 in epididymal regions 1-5, 6 in regions 6 and 7, and one in region 8. Two bands in samples from the efferent ducts were absent caudally, and one band present in region 7 was absent in region 8. The rates of incorporation of (35)S-methionine into minced duct in vitro varied among regions when expressed per milligram of wet weight of tissue (region 2-5 > region 7 > region 6 > region 1 > region 8 > ductuli efferentes), and orchidectomy had little effect on the rates. Incorporation into four proteins that were secreted in vitro (M(r) 38 000, 20 000, 15 000, and 13 000) was reduced or abolished by orchidectomy and restored by testosterone therapy. The secretion of three proteins (M(r) 52 000, 23 000, and 22 000) was reduced or abolished by orchidectomy and not restored by testosterone therapy. SDS-PAGE of detergent extracts of sperm indicated that five proteins were lost and nine were gained during epididymal transit. Seven of the proteins gained were about the same molecular weight as proteins secreted by the epididymis (M(r) 94 000, 52 000, 38 000, 36 000, 22 000, 20 000, and 13 000) and were analyzed using N-terminal amino acid microsequencing.

Rabbit Epididymal Secretory Proteins. II. Immunolocalization and Sperm Association of REP381

“…The results described here confirm our previous proposal [4] that REP38 is a protein that is synthesized and secreted by the epididymis. Use of a polyclonal antibody confirmed that REP38 is not present in tissues outside the epididymis and clarified that REP38 is only synthesized and secreted in regions 5 and 6 of the epididymis and persists caudally in the lumen.…”

“…The maturation process is dependent on sperm associating with specific proteins secreted by the epididymal mucosa under the influence of androgen [2,3]. In an earlier report on the rabbit [4], we identified a number of proteins secreted by the epididymal mucosa and their dependence on androgen. Here, we describe the isolation, characterization and immunolocalization of the most abundant of the secreted proteins that is present in luminal fluid from the cauda epididymidis, REP38, a protein of M r 38 000.…”

Post-testicular sperm maturation and identification of an epididymal protein in the Japanese quail (Coturnix coturnix japonica)

“…While the identity of these proteins remains to be established, they appear specific to Galliform birds and antibodies to them cross-react with quail spermatozoa (Esponda & Bedford 1985, Morris et al 1987. The binding of these proteins to the surface of sperm shares some analogy with the epididymal-driven modification of mammalian spermatozoa (Orgebin-Crist 1973, Orgebin-Crist & Jahad 1978, Nixon et al 2002b.…”

Identification and characterization of ERp29 in rat spermatozoa during epididymal transit

“…Throughout its length, the epididymis is able to create sequential changes in the composition of luminal fluid, e.g. ions, solutes, proteins, and lipids (Kirchhoff et al 1998, Nixon et al 2002, Saez et al 2003, Frenette et al 2004. The epithelial cells of the epididymis form a barrier to create a unique microenvironment in the lumen, where interactions between epithelial cells and spermatozoa take place via the fluid (Amann et al 1993, Dacheux et al 2003, 2005, Chan & Zhang 2005, Sullivan et al 2005.…”