EVALUATION OF ASCORBATE AND URATE ANTIOXIDANT CAPACITY IN HUMAN SEMEN

The ascorbate/urate ratio in the seminal plasma was studied in 76 rand omly chosen infertile men. The levels of ascorbate and urate were foun d to vary widely (range: 93-954 mu mol l(-1) and 127-670 mu mol l(-1), respectively), while the ascorbate/urate ratio was 1.03 +/- 0.63 (mea n +/- SD), indicating almost equimolar concentrations of both compound s in more than 60% of the subjects investigated. No relationship of as corbate with any biochemical marker of accessory sex gland secretions was observed, whereas an inverse correlation of urate with some prosta tic markers, acid phosphatase (-0.37; P<0.001), zinc (-0.35; P<0.002) and citric acid (-0.33; P<0.003), was found. In vitro experiments were conducted on an artificial suspension containing ascorbate and urate at physiological levels and activated polymorphonuclear leukocytes in the normal range (as proposed by WHO) to determine the extent to which the presence of superoxide anion-generating leukocytes contribute to the depletion of ascorbate and urate. The ascorbate level did not chan ge in the presence of 0.2 x 10(6) leukocytes ml(-1), while higher amou nts of activated polymorphonuclear leukocytes initiated ascorbate oxid ation, the intensity of which was in correlation with the extent of le ukocyte contamination. After incubation (37 degrees C, 30 min) in the presence of 0.4, 1.0 and 1.5 x 10(6) cells ml(-1) the average decline from the initial ascorbic acid level was 24, 43 and 49%, respectively. However, exposure of whole semen, instead of buffer, to oxidants rele ased from the same amount of activated polymorphonuclears led to only 2.6, 11 and 22% decrease of the ascorbic acid, most probably due to th e action of other superoxide anion scavenger compounds present in seme n. Excessive superoxide anion production due to the presence of activa ted leukocytes had no influence on urate level either in the artificia l suspension or in semen. The ability of ascorbate to afford protectio n against leukocyte-associated superoxide anions is not hampered in th e semen of infertile men, provided that leukocyte contamination does n ot exceed 1 x 10(6) cells ml(-1) The possible role of urate in stabili zing the ascorbate antioxidant activity in seminal plasma should be fu rther investigated.