[Zinc concentrations and total amount of zinc in seminal plasma of infertile men with special reference to prostatic secretory function].

The exact relationship between seminal plasma zinc and fertility is not known. Zinc is secreted mainly by the prostate, and zinc concentration in seminal plasma is regarded as an excellent indicator of prostatic secretory function. However, low zinc concentration may result not only from poor secretory function of the prostate but also from dilution due to excessive secretion of seminal vesicular fluid. This assumption is supported by the present result that zinc concentration was inversely correlated with fructose concentration. Therefore zinc concentration is thought to reflect prostatic function in proportion to seminal vesicular function. Total amount of zinc in seminal plasma seems to be an appropriate indicator for prostatic secretory function. In the present study, concentrations and total amount of zinc were examined in seminal plasma of men with various fertility problems. There were no significant differences between men with normal spermodiagram and those with abnormal spermodiagram, seminal inflammation or varicocele in concentration or total amount of zinc. No changes were observed in any of them after various therapies including oral zinc sulfate. However, the percentage of men with normal spermodiagram was low in the group with extremely low or high zinc concentration and total sperm count tended to increase with increase in total amount of zinc. Furthermore, the spermatozoal motility was better in the prostatic fraction than in the vesicular fraction of split ejaculates, and the percentage of men with decreased motility and normal sperm concentration was significantly high in the group with lower zinc concentration or decreased total amount of zinc. These observations indicate that prostatic secretion has a stimulatory effect on spermatozoal motility. The secretory activities of the prostate and the seminal vesicle are generally known to be closely controlled by androgens, but our findings indicate that the secretory functions of these accessory organs are independent because there was no correlation between total amount of zinc and fructose. Analysis of the relative concentrations in prostatic secretion, split ejaculates, and seminal plasma confirmed an almost exclusively prostatic origin of zinc. As part of the routine andrologic examination, measurement of concentration and total amount of zinc in seminal plasma is useful for evaluating prostatic function, but measurement of acid phosphatase, magnesium, calcium or potassium will provide almost as much information, since they also seem to be secreted primarily by the prostate.