Sperm plasma membrane integrity in fertile and infertile men.

Sperm plasma membrane characteristics were analysed by a combined method, the HOS-eosine test (HOS-E test), that consists of the hypoosmotic swelling test (HOS test), and the eosine-Y staining. Semen samples were categorized into four groups (Normo-, Oligo-, Astheno-, and Oligoasthenozoospermic) and subjected to the standard analysis (spermiogram), HOS test, eosine-nigrosine test (reflecting sperm viability); and HOS-E test. HOS-E test makes it possible to distinguish four groups of spermatozoa: type 1, HOS+/eosine-; type 2, HOS-/eosine-; type 3, HOS-/eosine+; and type 4, HOS+/eosine+. Normozoospermic samples showed 61.2 +/- 1.4% type 1, 9.2 +/- 0.8% type 2, 22.6 +/- 1.1% type 3, and 6.8 +/- 0.6% type 4 spermatozoa. Oligozoospermic samples showed no significant differences in these values, whereas asthenozoospermic samples showed a higher percentage of types 3 and 4 and a lower percentage of type 1. Oligoasthenozoospermic samples showed high percentages of types 2, 3, and 4 and a low percentage of type 1. Sperm plasma membrane integrity is a necessary condition for motility and fertilization. So, it is not surprising that semen samples with abnormal motility showed a HOS-E result indicative of a defective plasma membrane.