IN-VITRO EFFECT OF ZINC ON OXIDATIVE CHANGES IN HUMAN SEMEN

The in vitro effect of zinc on superoxide anion (O-2(-)) generation an d on experimentally induced lipid peroxidation (LPO) in spermatozoa of infertile men was investigated. Washed spermatozoa pre-incubated for 30 min at 37 degrees C in the presence of 1 or 3 mmol l(-1) zinc, rele ased less superoxide anions (P<0.03 and P<0.02, respectnlely; n=9) tha n the untreated spermatozoa. Similar results were obtained using activ ated polymorphonuclear leukocytes (1 x 10(6) cells ml(-1)) in the pres ence of 1 or 3 mmol l(-1) Zn (P<0.001 and P<0.0002, respectively; n=9) . The in vitro evidence of the inhibitory effect of zinc on O-2(-) gen eration by human spermatozoa and leukocytes indicates that zinc may ac t in vivo as a scavenger of excessive O-2(-) production by defective s permatozoa and/or leukocytes in semen after ejaculation. A significant stimulatory effect of Zn (3 mmol l(-1)) on iron-induced lipid peroxid ation, measured by the formation of thiobarbituric acid reactive subst ances (TBARS), was detected in the spermatozoa of 16 normo- and 17 ast henozoospermic males (P<0.0001 and P<0.001, respectively). In 11 sampl es with sperm concentration 20.3 +/ - 2.1 x 10(6) ml(-1), exhibiting i nitial TEARS concentration two times higher than in normo- and astheno zoospermic samples (40.5f2.4 vs. 17.1+/-1.1 and 28.5+/-4.1 nmoles TBAR S 10(-8) spermatozoa), no effect of zinc on the LPO rate was found. Th e observed inhibitory effect of zinc on superoxide anion regardless of the initial O-2(-) level and stimulatory effect of zinc depending on the initial LPO rate in human spermatozoa suggests that this metal ion participates in the oxidative changes occurring after ejaculation and thus may modulate the properties of germ cells.