Superoxide anion scavenging capacity of human seminal plasma.

This study has investigated the antioxidant capacity of human seminal plasma due to the presence of both high and low molecular weight antioxidant factors. Methods for the measurement of superoxide dismutase-like activity (SOD-like) and total antioxidant status (TAS) were automated, and had a within-run coefficient of variation of 7.3% for SOD-like activity and 4.8% for TAS. In 69 semen samples from unselected infertile men, SOD-like activity in seminal plasma ranged from 2 to 16 U/ml, with a mean of 6.9 +/- 2.8 U/ml. As SOD-like activity was correlated positively with levels of citric acid (p < 0.0001), zinc (p < 0.0002) and acid phosphatase activity (p < 0.0005), and there was no correlation with fructose levels, our results suggest that prostatic secretions are an important source of superoxide anion scavengers. Evaluation of SOD-like activity in infertile men with accessory sex gland infections (n = 12) showed significantly lower activity (p < 0.003) compared to values found in 12 infertile men without signs of infection. The values obtained for total antioxidant status (equivalent to the antioxidant capacity of alpha-tocopherol analogue) ranged from 1.7 to 2.3 mmol/L, with a mean of 2.1 +/- 0.1 (n = 40), reflecting the protective activity of ascorbate, urate and albumin, and to a very low extent of glutathione and taurine. The data obtained by TAS assay correlated with fructose, a major marker of vesicular secretion (p < 0.005), suggesting that low molecular weight components with antioxidant capacity derive partly from the seminal vesicles. The results indicate that the relative contribution of antioxidant defence systems capable of counteracting the deleterious action of superoxide anions, depends on the secretory activity of accessory sex glands and is independent of excessive ROS production due to increased oxidative stress.