THE SPERMATOZOAL VOLUME AS INDICATIVE OF THE PLASMA-MEMBRANE INTEGRITY (MODIFICATION OF THE HYPOOSMOTIC SWELLING TEST) .1. METHODS

The aim of the present study was to establish a more differentiating i ndicator of plasma membrane integrity of spermatozoa than the classic version of the hypoosmotic swelling test according to Jeyendraan. Sper matozoa were prepared by density gradient centrifugation (90% Percoll) to select 'fertilization competent' spermatozoa only. After a second washing procedure sufficiently pure sperm cell suspensions were obtain ed. The volume distributions of these sperm cells were measured with a Coulter Counter at 25 degrees C after adaptation in 300 mosmolar NaC1 solution resp. 150 mosmolar NaC1 solution for 5 min. These volume dis tributions showed significantly different patterns for the isotonic an d hypotonic stress situation in the simple salt solution. Moreover, th e comparison of the response to hypoosmotic stress showed more than fo ur reproducible characteristic patterns, promising well differentiated results for different sperm populations. The new method for the detec tion of hypoosmotic swelling effect might be a real and valuable funct ional parameter.