Egg water from thr amphibian Bufo arenarum induces capacitation-like changes in homologous spermatozoa

DARÍO KRAPF,; VISCONTI, P.; SE ARRANZ,; CABADA, MARCELO OSCAR

Developmental Biology

Año: 2007 p. 516 - 524

0012-1606

Mammalian sperm acquire fertilizing capacity after residing in the female tract, where physiological changes named capacitation take place. In animals with external fertilization as amphibians, gamete interactions are first established between sperm and molecules of the egg jelly coat released into the medium. Since dejellied oocytes are not normally fertilized, the aim of this study was to determine if the jelly coat of the toad promotes a “capacitating” activity on homologous sperm. We found that incubation of sperm in diffusible substances of the jelly coat (named Egg Water) for 90-180 sec is sufficient to render sperm transiently capable of fertilizing dejellied oocytes. Similar to mammalian sperm, the fertilizing state was correlated with an increase of protein tyrosine phosphorylation and a decrease of the sperm cholesterols content. Inhibition of both events, increase in tyrosine phosphorylation as well as cholesterol efflux, affected the acquisition of fertilizing capacity. Phosphorylation and fertilization could be promoted with NaHCO3, and also by addition of beta cyclodextrin, a cholesterol binding compound. Moreover, sperm could gain the ability to fertilize dejellied oocytes in vitro in the presence of these compounds. These data indicate that Bufo arenarum sperm should undergo a series of molecular changes to gain fertilizing capacity; these changes are reminiscent of mammalian sperm capacitation.