CORRELATION BETWEEN THE RATE OF LIPID-PEROXIDATION AND CELLULAR MATURITY AS MEASURED BY CREATINE-KINASE ACTIVITY IN HUMAN SPERMATOZOA

We have demonstrated previously that creatine kinase (CK) activity is a measure of cellular maturity and fertilizing potential in human sper matozoa. In the present work we have examined whether there is a relat ionship between sperm CK activity and the rate of lipid peroxidation ( LP) as measured by malondialdehyde (MDA) formation. Both MDA productio n and CK activity were higher in oligospermic than in normospermic spe cimens (P < 0.001, N = 41 and 101, respectively), and there was a clos e correlation (R = 0.43, P < 0.001) between these two biochemical para meters. As demonstrated previously with the CK measurements, there was a heterogeneity among the groups: About 40% of the oligospermic men h ad MDA and CK activity values similar to that of the normospermic grou p, and 12% of the normospermic men had MDA and CK activity values simi lar to that of the oligospermic group. We have also examined in three experimental paradigms the question of sperm-to-sperm propagation of i ncreased LP and the possible increase in LP following centrifugation a s used in sperm preparation for assisted reproduction: The MDA differe nces among Percoll sperm fractions originating within the same specime ns, the lack of change in MDA production after co-centrifugation and c o-incubation or samples with high and low sperm LP rates, and the repe ated centrifugation of the same specimens without an increase in MDA p roduction all indicated the lack of sperm-to-sperm propagation of LP o r increase in LP due to mechanical stress. However, the iron content o f Ham's F-10 medium or iron added to human tubal fluid medium has sign ificantly increased the rate of LP in various sperm samples. Exposure to iron during sperm preparation procedures in assisted reproduction i s likely to affect sperm integrity and fertilizing potential. We can c onclude that there are highly significant differences in the rate of L P among men and among sperm within the same specimen. We suggest, base d on the relationship between LP and CK activity, that the increased r ate of LP along with the increased CK content are due to incomplete cy toplasmic extrusion during terminal spermatogenesis. The retained exce ss cytoplasm in immature sperm fuels LP. Thus, the increased rate of s pontaneous LP is an ''inborn'' rather than an ''acquired'' property of spermatozoa.