SHORT COMMUNICATION Altered malondialdehyde, protein carbonyl and sialic acid levels in seminal plasma of microscopically abnormal semen A. Saraniya 1 , B. C. Koner 1 , P. Doureradjou 1 , N. Selvaraj 1 & V. Shivagourou 2 1 Department of Biochemistry, Jawaharlal Institute of Postgraduate Medical Education & Research, Pondicherry, India; 2 Department of Pathology, Jawaharlal Institute of Postgraduate Medical Education & Research, Pondicherry, India Introduction About 8–10% of couples experience some sort of infertil- ity in their reproductive lives. Male infertility occurs mainly due to deficiency of active motile sperm count in semen. Reactive oxygen species (ROS) in semen have a potential role in normal fertilisation (Agarwal et al., 2006), but high levels of ROS in semen damage the sper- matozoa, which results in infertility (Aitken, 1994). Levels of malondialdehyde (MDA) and protein carbonyl (PC) indicate damage of lipids and proteins respectively by ROS. Sialic acid (SA) of glycoproteins was reported to pro- tect the proteins from ROS (Eguchi & Ikeda, 2005). Many sialo-proteins are claimed to take part in the fertilisation process (Rajalakshmi et al., 1997). Oxidative stress may increase the sialyl transferase activity (Resenberg, 1999) and increase the SA content of seminal proteins. The microscopical examination of the semen is most widely used in male infertility. The search for markers that can complement/supplement the existing one is on. Hence, the present study was designed to compare MDA, PC and SA levels of seminal plasma in microscopically normal and abnormal semen and to establish their poten- tial as markers of abnormal semen. Materials and methods The study included 50 male subjects who came to JIPMER, Puducherry, India, for primary infertility and were advised for semen analysis. Men with a history of infections, smoking, alcoholism, drug therapy and other known cause of infertility were excluded from the study. Semen analysis was performed according to guidelines of the World Health Organization (1999). Low sperm count and/or motility were considered as abnormal semen (n = 26). Then, the liquefied semen samples were centri- fuged and the supernatant was stored at )80 °C for fur- ther analysis. Malondialdehyde was measured by thiobarbituric acid (TBA)–trichloroacetic acid–HCL method (Niehaus & Samuelsson, 1968), PC was measured spectrophotometri- cally by 2,4–dinitrophenyl hydrazine (Levine et al., 1994) and SA was estimated using TBA (Aminoff, 1961). Data were expressed as mean and SD. Comparison and correlation of data were performed by Student’s t-test Keywords Carbonylation—male infertility— malondialdehyde—protein bound sialic acid—seminal plasma Correspondence Dr B. C. Koner, Department of Biochemistry, JIPMER, Dhanvantri Nagar, Gorimedu, Pondicherry 605006, India. Tel.: +91 413 227 3116; Fax: +91 413 227 2067; E-mail: bckoner@hotmail.com Accepted: October 17, 2007 Summary Microscopically abnormal (n = 26) semen showed significantly higher levels of malondialdehyde (MDA), protein carbonyl (PC) and protein-bound sialic acid (SA) in seminal plasma as compared with normal semen (n = 24). The per- centage of nonmotile spermatozoa showed significant (P < 0.01) positive corre- lation with MDA (r = 0.5) and PC (r = 0.49). Sperm counts showed a significant negative correlation with MDA (r = )0.63, P < 0.001) level of semi- nal plasma. SA correlated (r = 0.56, P < 0.01) with MDA. The receiver operat- ing characteristic (ROC) curve of MDA and SA showed that MDA of 3.15 lmol l )1 and SA of 3.85 lmol l )1 were optimum cut-off limits to discrim- inate abnormal semen from normal. In conclusion, high SA might be a protec- tive response against prevailed oxidative stress in abnormal semen. Seminal plasma MDA and SA may act as potential markers of abnormal semen. ª 2008 The Authors 56 Journal Compilation ª 2008 Blackwell Publishing Ltd Andrologia 40, 56–57