Zinc and zinc ligands in human seminal plasma. II. Contribution by ligands of different origin to the zinc binding properties of human seminal plasma.

The zinc binding properties of whole human seminal plasma and various fractions of split ejaculates were analysed with gel chromatographic and dialysis methods. The proportion of dialyzable zinc was strongly correlated to the zinc/fructose ratio in the seminal plasma, i.e. correlated to the relative contributions by the prostate and seminal vesicles, respectively. Zinc originates, however, almost entirely from the prostate gland. The non-diffusible zinc ligands thus seemed to originate from the seminal vesicles. This could also be confirmed in experiments with split ejaculates. The high molecular weight (HMW) zinc ligands from the seminal vesicles have also a higher affinity for zinc than the low molecular weight (LMW) ligands from the prostate. A redistribution of zinc therefore takes place after ejaculation. The HMW zinc ligands from the seminal vesicles were found to have an isoelectric point at 6.1-6.7, to be glucoproteins, and to have an apparent molecular weight of 250,000. The possible physiological implications of a redistribution of zinc after the ejaculation is discussed in view of the fact that zinc is of importance for many functional properties of the human spermatozoa.