Correlation Between the Rate of Lipid Peroxidation and Cellular Maturity as Measured by Creatine Kinase Activity in Human Spermatozoa

Abstract

ABSTRACT: We have demonstrated previously that creatine kinase (CK) activity is a measure of cellular maturity and fertilizing potential in human spermatozoa. In the present work we have examined whether there is a relationship between sperm CK activity and the rate of lipid peroxidation (LP) as measured by malondialdehyde (MDA) formation. Both MDA production and CK activity were higher in oligospermic than in normospermic specimens (P < 0.001, N = 41 and 101, respectively), and there was a close correlation (R = 0.43, P < 0.001) between these two biochemical parameters. As demonstrated previously with the CK measurements, there was a heterogeneity among the groups: About 40% of the oligospermic men had MDA and CK activity values similar to that of the normospermic group, and 12% of the normospermic men had MDA and CK activity values similar to that of the oligospermic group. We have also examined in three experimental paradigms the question of sperm‐to‐sperm propagation of increased LP and the possible increase in LP following centrifugation as used in sperm preparation for assisted reproduction: The MDA differences among Percoll sperm fractions originating within the same specimens, the lack of change in MDA production after co‐centrifugation and co‐incubation of samples with high and low sperm LP rates, and the repeated centrifugation of the same specimens without an increase in MDA production all indicated the lack of sperm‐to‐sperm propagation of LP or increase in LP due to mechanical stress. However, the iron content of Ham's F‐10 medium or iron added to human tubal fluid medium has significantly increased the rate of LP in various sperm samples. Exposure to iron during sperm preparation procedures in assisted reproduction is likely to affect sperm integrity and fertilizing potential. We can con‐clude that there are highly significant differences in the rate of LP among men and among sperm within the same specimen. We suggest, based on the relationship between LP and CK activity, that the increased rate of LP along with the increased CK content are due to incomplete cytoplasmic extrusion during terminal spermatogenesis. The retained excess cytoplasm in immature sperm fuels LP. Thus, the increased rate of spontaneous LP is an “inborn” rather than an “acquired” property of spermatozoa. 1994 American Society of Andrology