Several recent reports have suggested that the sperm counts of normal men are declining in most countries. In this study the sperm counts of Finnish men, and their possible changes during the past 28 years, were investigated. The material consisted of semen samples from 238 normal healthy men of unknown fertility and 5481 men from infertile couples. The means (medians) of semen volume, sperm density and total sperm count in normal men were 3.3 (3.0) ml, 133.9 (94.0) x 10(6)/ml and 396.6 (309.0) x 10(6), respectively. These parameters and the relative frequency distribution of the sperm density were similar to those reported elsewhere in the 1940s. Multiple linear regression analysis revealed a significant decrease in semen volume, whereas sperm density and total sperm count of infertile men had not changed significantly during the past 28 years. In addition, no change in sperm counts was associated with the year of men's birth.

The concentrations of lead, magnesium, selenium and zinc in seminal fluid from men with variable semen quality (sperm morphology, density and motility) and fertility were determined by atomic absorption spectrometer without or with Zeeman background correction. The mean (+/- SD) concentration of selenium in the samples (n = 142) was 28.8 +/- 9.5 micrograms/l, which was about a third of the corresponding serum value (77.8 +/- 13.3 micrograms/l, n = 140). The serum selenium level was significantly (P less than 0.001) higher in infertile than in fertile men, but the seminal fluid did not show such a difference. No correlation was obtained between selenium values in seminal plasma and sperm density or motility. The levels of lead in seminal fluid were very low with no correlation to the levels of magnesium, selenium and zinc or the semen qualities. The seminal fluid lead concentration was significantly (P less than 0.001) higher in infertile (3.6 +/- 3.2 micrograms/l, n = 79) than in fertile men (1.7 +/- 1.0 micrograms/l, n = 39). Magnesium (103.5 +/- 49.2 mg/l, n = 90) and zinc (141.1 +/- 71.7 mg/l, n = 157) concentrations in seminal fluid were comparable with previous reports. Both minerals showed a positive correlation to the seminal fluid selenium, while only zinc displayed a borderline correlation with sperm density. The present findings indicate that the determination of seminal fluid selenium may not offer any advantages over zinc and magnesium measurement in the fertility assessment and its role in human semen remains obscure. The low lead concentrations in the present material is a clear indication of low industrial exposure.

High levels of selenium and glutathione peroxidase (GSH-Px) were found in bull seminal plasma but low concentrations in human seminal plasma. In man the seminal plasma selenium was associated with two macromolecules separable by gel filtration, but no GSH-Px was found in the same fractions. Selenium in bull seminal plasma was associated with two proteins, which could be separated by gel filtration and anion exchange chromatography. Both macromolecules coeluted with GSH-Px activity and had identical optima at pH 7.0. Their responses to thermal treatment, however, differed. Seminal vesicle secretory fluid in the bull contained both these proteins, while the larger molecule was also found in fractionations of ampulla, prostate and Cowper's glands. The larger enzyme form is evidently a tetramer of the smaller one. Both enzyme forms were extremely sensitive to heavy metals and some divalent metal ions. GSH caused an activation while other reducing agents were suppressive. Triton X-100 had no effect, while sodium deoxycholate was inhibitory. These properties are typical for a phospholipid hydroperoxide GSH-Px. It is concluded that this selenium-dependent enzyme may be important in the protection of bovine spermatozoa against damage caused by oxygen radicals, while in man such a mechanism is not functional.

Selenium (Se) and glutathione peroxidase (GSH-Px) were determined from the seminal plasma samples and spermatozoa of human and four different animal species. The human sperm Se concentration was 1.8 +/- 0.8 micrograms/g dry weight, which was about half of that in the bull. Abnormal sperm morphology and motility correlated with low sperm Se content. The volume of sperm mitochondrial sheath in human, bull and stallion was measured using transmission electron microscopy. In these species the sperm Se content was highly correlated with the volume of mitochondria. Among the five species studied, the seminal plasma level of Se was lowest in human male and stallion, while the highest levels were encountered in the bull. No correlation was obtained between human semen quality and seminal plasma Se concentration. The seminal plasma GSH-Px activity was low in man and ram, absent in boar and stallion but very high in the bull. The amount of structural sperm Se as well as seminal plasma Se and GSH-Px activity appears to be highly variable in different species.

Objective: To assess differences in semen quality between similar populations from Denmark and Finland. Design: Comparison of semen quality between 221 Finnish men (of whom 115 had no proven fertility) and 411 Danish men with no proven fertility in two follow-up studies among normal couples trying to conceive. Methods: In Finland male partners of couples without experienced infertility attempting to conceive were recruited through advertisements in local newspapers from 1984 to 1986. From 1992 to 1995 Danish men who lived with a partner and who had not attempted to achieve a pregnancy previously were recruited through their union when they discontinued birth control. All semen analyses were performed in accordance with the World Health Organization guidelines. Results: Median sperm concentration, total sperm count and the percentage of morphologically normal spermatozoa were significantly higher among the Finnish men without proven fertility (104.0 million/ml, 304.0 million and 58% respectively) compared with the Danish men (53.0 million/ml, 140.8 million, and 41% respectively). Sperm concentration was 105.7% (95% confidence interval (CI) 58.1%-167.6%) and total sperm count was 127.4% (95% CI 71.4%-201.6%) higher among Finnish men without proven fertility than among Danish men after control for confounders. Conclusions: Some, but hardly all, of the observed difference in semen quality may be explained by differences in recruitment procedures, selection of the men and by methodological differences in semen analysis between the two countries. Also a birth cohort effect may explain some of the differences between countries as the Finnish men were recruited 11 years before the Danish men. Therefore, follow-up studies with identical recruitment and selection of men from the two countries are needed.