| Abstrakt: |
The role of hyaluronidase, beta-glucuronidase and beta-N-acetylglucosaminidase in the penetration by mouse spermatozoa through the layers surrounding the oocyte was investigated by in vitro techniques. Myocrisin, fenoprofen, phosphorulated hesperidin and PS53 (a hydroquinone-sulfonic acid-formaldehyde polymer) inhibited fertilization when incubated with capacitated spermatozoa before the treated spermatozoa were mixed with intact oocytes but not when the inhibitor-treated, capacitated spermatozoa were added to oocytes free of follicle cells. The antifertility activity did not appear to be due to an effect on sperm motility or on the oocytes. These 4 compounds are known hyaluronidase inhibitors and, of the acrosomal enzymes tested, only share inhibition of hyaluronidase. Kinetic studies indicated that myocrisin is a reversible inhibitor of mouse sperm hyaluronidase whereas the other three are irreversible inhibitors. Adding saccharolactone, a beta-glucuronidase inhibitor, or N-acetylglucosaminolactone and N-acetylgalactosaminolactone, beta-N-acetylglucosaminidase inhibitors, to capacitated spermatozoa under the same conditions as the hyaluronidase inhibitors did not decrease fertilization. This was the case even though the beta-glucuronidase or beta-N-acetylglucosaminidase activities of the spermatozoa were completely inhibited, at least at the time that the inhibitor-treated, capacitated spermatozoa were mixed with the oocytes. The hyaluronidase activity of mouse spermatozoa remained unaltered during the incubation period required for capacitation; however, prolonged incubation caused a significant decrease in hyaluronidase. Untreated mouse spermatozoa caused hydrolysis of hyaluronic acid more effectively than did sperm extracts obtained by detergent extraction. These results are consistent with the theory of an essential role of hyaluronidase in mouse fertilization. At least in this species, the enzyme appears to be specifically involved in sperm penetration through the follicle cell layer. The data do not support an essential role for beta-glucuronidase and beta-N-acetylglucosaminidase in the penetration by mouse spermatozoa through the oocyte's investments. In contrast to some other species, sperm capacitation in mice does not result in a loss of hyaluronidase although part of the enzyme activity is lost on prolonged incubation. Mouse spermatozoa appear to be able to digest substrate (hyaluronic acid) even though hyaluronidase is not released. |
