Male accessory sex glands produce heparin‐binding proteins that bind to cauda epididymal spermatozoa and are testosterone dependent

Abstract

Heparin binds to bovine sperm and stimulates capacitation in vitro. Seminal plasma alters the ability of epididymal sperm to bind heparin, and several heparin-binding proteins (HBPs) have been identified in bull seminal plasma. This study had three objectives: 1) to identify production sites of seminal plasma HBPs, 2) to determine which HBPs bound to cauda epididymal sperm, and 3) to determine whether presence of HBPs was testosterone dependent. Proteins from bull or rat seminal vesicles, prostates, and bulbourethral glands were separated by heparin affinity high-performance liquid chromatography. HBPs were found in all accessory glands of rats and bulls, but the major source of bovine seminal plasma HBPs appeared to be seminal vesicles. Between 25% and 50% of the protein from each gland bound to the heparin column, and NaCl concentrations required to elute proteins ranged from 0.15 to 1.4 M. One-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that major HBPs were relatively small, with molecular weights between 13 and 31 kDa, but some HBPs also exhibited higher molecular weights, between 40 and 100 kDa. Radioiodinated HBPs from each bovine gland were incubated with epididymal sperm. Labeled HBPs binding to sperm exhibited molecular weights of 14, 16, 24, and 30 kDa as determined by SDS-PAGE and autoradiography. The HBP content of the accessory sex glands decreased significantly in castrated rats and was restored to levels of sham-operated controls by testosterone replacement. Heparin-binding proteins may play a role in fertilization by attaching to sperm surfaces, enabling heparin-like glycosaminoglycans in the female reproductive tract to induce capacitation.

Electrophoretic profile of boar seminal proteins

“…Sperm proteins were extracted as per the method described by Nass et al (1990) with slight modifications. The sperm pellets were thawed to room temperature and washed twice with 1 ml of TC buffer at 5°C.…”

Carbohydrates and fertilization in animals

“…These heparin-binding proteins were divided into three families of proteins having molecular weights of 14-18, 24, and 31 kDa, but it is not known whether these proteins are related to each other. They are mainly products of the seminal vesicles and their production is testosterone dependent (Nass et al, 1989). The 14 to 18-kDa proteins are similar in molecular weight to fibronectin-like polypeptides which are major components of bovine seminal plasma (Esch et al, 1983;Baker, 1985;Majunath and Sairam, 1987;Seidah et al, 1987).…”

Seminal Plasma Proteins as Potential Markers of Relative Fertility in Zebu Bulls (Bos taurus indicus)

“…Other studies have shown that accessory glands produced and secreted HBP into seminal fluid , and HBP bound to sperm at ejaculation (Miller et al, 1990;Nass et al, 1990). Miller et al (1990) reported that HBP constituted 28% of the protein component of seminal fluid or approximately 19.6 mg HBP/mL of ejaculate, and HBP-B5 constituted 6% of the total HBP in fluid from vasectomized bulls.…”

“…Sperm from high-fertility bulls have a greater frequency of acrosome reactions in response to heparin-like material (Lenz et al, 1988). Heparin-binding proteins (HBPs) are produced by the male accessory glands, secreted into seminal fluid (Nass et al, 1990). Fertility for Group 1 (HBP-B5) in sperm membranes but undetectable HBP-B5 in seminal fluid) was 82% of 1,692 cows.…”