Release, extraction, and stability of hyaluronidase associated with human spermatozoa. Comparisons with the rabbit

In contrast to the rabbit: 1) no hyaluronidase could be detected in fresh or frozen human seminal plasma, all color formation on assay being due to a dialyzable, heat stable factor; 2) almost no hyaluronidase could be extracted from frozen-thawed human testicles; 3) the hyaluronidase from human spermatozoa was rapidly inactivated upon release, either spontaneously or on extraction; and 4) a large decrease in hyaluronidase activity occurred when human spermatozoa were stored under various conditions. Rabbit spermatozoa contained six to 13 times more hyaluronidase than human spermatozoa. These results show that distinct species differences exist in the hyaluronidase associated with spermatozoa. None of the human genital tract sources studied could be used to obtain adequate amounts of hyaluronidase for the further isolation and purification of the enzyme. For both human and rabbit spermatozoa, it was optimal to add the cells directly to the assay system for the quantitation of hyaluronidase on spermatozoa rather than extracting the spermatozoa and testing the extracts. The spermatozoa of both species appear to be capable of digesting hyaluronic acid directly. As had previously been found for acrosin, a higher amount of hyaluronidase was maintained when human spermatozoa were cryopreserved in a zwitter buffer (TESTCY) rather than in glycerol.