The correlates of fertilizing capacity in normal fertile men.

An investigation has been carried out in normal fertile men on the correlates of fertilizing capacity as defined by the zona-free hamster egg penetration test. The results demonstrate that the apparent fertility of these men is compatible with a wide range of intrinsic sperm quality as reflected by penetration rates ranging from 14% to 90% and differences in the minimum concentration of motile spermatozoa required to initiate penetration. These differences in sperm function could not be correlated with any of the conventional parameters of semen analysis or any of a large number of sperm movement characteristics analyzed by time-exposure photomicrography, with two exceptions: (1) the percentage of progressively (greater than 25 micron/sec) motile spermatozoa exhibiting an amplitude of lateral head displacement (Ah) of less than 10 micron, which was positively correlated with penetrating capacity (P less than 0.01), and (2) the percentage of progressively (less than 25 micron/sec) motile spermatozoa exhibiting an Ah of greater than 10 micron, which was negatively correlated with penetration rate (P less than 0.05). The information obtained in this study should provide a useful basis against which to compare the properties of spermatozoa in cases of suspected infertility.