The formation of malondialdehyde (MDA), a product of lipid peroxidation (LPO), was measured in human spermatozoa from 27 subjects with normal sperm characteristics. Peroxidation of lipids in washed spermatozoa was induced by catalytic amounts of ferrous ions and ascorbate and malondialdehyde determined by thiobarbituric method. MDA formation varied considerably from one sample to another. The studied population showed a strong correlation between lipid peroxidation potential (amount of MDA formed by 10(8) spermatozoa after 1 hour of incubation) and 1) initial motility r = -0.623, P = 0.001; and 2) morphologic abnormalities of the midpiece r = 0.405, P = 0.05. These results suggest that poor motility is linked with membrane fragility and that spermatozoa with midpiece abnormalities probably have membrane and/or cytoplasmic antiperoxidant system defects. Because LPO potential is related to the two most important characteristics of fertility, it seems possible that it has the potential to become a good biochemical index of semen quality.

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Summary. The within-subject variability of the semen sperm count (n), volume (v) and the total number of spermatozoa (N) was studied on 220 ejaculates from 36 normal subjects after an abstinence of 7 days or less. For each of the three variables, the within-subject standard deviation , \g=s\, was practically proportional to the mean, \ g=m\ ; the common value of the coefficient of variation \ g=s\ / \ g=m\ for all subjects was very high: 0\m=.\39for n, 0\m=.\28for v and 0\m=.\55for N. The 95% confidence intervals based on a single ejaculate were asymmetrical and very large, the lower and upper limits being respectively 0\m=.\5\ m=x\n and 2\m=.\3\ m=x\ n; 0\m=.\7\ m=x\v and 1\m=.\8\ m=x\ v; 0\m=.\4\ m=x\N and 2\m=.\9\ m=x\N. The three semen characteristics for a given subject were highly correlated with the length of abstinence: for an increase in abstinence of 1 day there were mean increments of 13 \m=x\ 106/ml for n, 0\m=.\4ml for v, and 87 \m=x\106 for N.