Background:   Redox regulation is important for maintaining oocyte quality. In vitro mammalian fertilization studies show higher percent development when treated to increase oocyte [GSH] (1,2). Age-related decreases in human fertility may be affected by oocyte GSH:GSSG ratios (3). Could glutathionergics signal quality of female oocytes? We studied a model system, the marine worm Alitta (formerly Nereis) succinea, in which females use cysteine-glutathione-disulfide (CySSG), an oxidized form of glutathione, as a pheromone to arouse males (4).

Methods: Mature females of A. succinea were assessed for oocyte [GSH], fertilization and development, and pheromone excretion after swimming for 1 min, 4 hr, & 24 hr. GSH was measured by HPLC in oocyte extracts. Oocytes from mature females chemically induced to spawn and fertilized by fresh sperm were assessed for first cleavage by one hour and trochophore stage by 48 hr. Pheromone release into swim media at 4 hr and 24 hr was measured by male response assay (as in (5)). 

Results: GSH in oocytes decreased significantly over swim time, from 1.9 mM to <0.3 mM at 24 hr (ANOVA, p<0.0001). Capability of oocytes to be fertilized and develop to trochophore decreased from 92% and 80%, respectively, initially, to <20% and 5% at 24 hr (p<0.001). CySSG excretion decreased from 50 ug/h (first 4 hr) to <5 ug/hr at 24 hr (p<0.0001). Additional data is available about conversion of radioactive GSH into CySSG, and coelomic fluid concentrations of glutathionergics.

Conclusion: A. succinea signals readiness to spawn with high quality oocytes with excretion of a physiologically costly chemical, derived from glutathione. Comparative physiology questions arise about whether cervicovaginal secretions derived or affected by redox regulators may similarly be used as indicators of oocyte quality.