A SOLUBLE EXTRACT FROM HUMAN SPERMATOZOA ACTIVATES ASCIDIAN OOCYTES

A soluble extract from human spermatozoa induced calcium oscillations and extrusion of the first polar body when injected into oocytes of th e ascidian Ciona intestinalis. The properties of calcium oscillations and time of polar body extrusion precisely mimic oocyte activation ind uced by C. intestinalis sperm or sperm extracts. The data suggest that human sperm extracts can activate oocytes of different phyla by the s ame mechanism as homologous spermatozoa. Injection of inositol 1,4,5-t risphosphate (IP3) into C. intestinalis oocytes mimicked to some exten t the initial stages of oocyte activation, but the results demonstrate that ascidian oocyte activation by human sperm extract cannot be expl ained solely in terms of IP3-induced calcium release. Injection of oth er calcium releasing second messengers, cyclic adenosine diphosphate r ibose, or calcium ions, does not lead to oocyte activation or release intracellular calcium in ascidian oocytes. It was concluded that human spermatozoa contain one or more molecules that can trigger intracellu lar calcium release in oocytes from different phyla.