Zinc and Zinc Ligands in Human Seminal Plasma

The occurrence of zinc ligands in human seminal plasma has been studied with gel filtration techniques. With an eluant of 0.05 M Tris with 0.15 M NaCl, pH 7.4, a mean of 11.6% of the zinc was bound to ligands with a molecular weights > 80 000 (HMW), 26.9% to ligands with molecular weights between 3000 and 80 000 (IMW), and 61.5% to ligands with molecular weights < 3000 (LMW), respectively (N = 21). Under standardized conditions the results were highly reproducible. There was a significant shift of zinc from HMW to LMW ligands if pH was less than 7 or higher than 8, or if phosphate ions were present. There was a temperature dependent shift of zinc from IMW towards LMW ligands indicating an enzymatic degradation of the IMW ligands. HMW was not changed with time if the semen samples were kept at room temperature for up 24 h. Despite a prostatic origin of zinc in human seminal plasma there was a co-variation between the fructose concentration (a vesicular marker) and zinc bound to HMW, i.e. the higher the fructose concentration the more zinc was recovered from the HMW-ligands. If HMW originates from the seminal vesicles this indicate a post-ejaculatory re-distribution of zinc between different ligands.