Developmental competence and glutathione content of maternally heat-stressed mouse oocytes and zygotes
The loss of developmental competence and the glutathione (GSH) content of maternally heat-stressed mouse oocytes and zygotes were determined. In experiment 1, zygotes were collected from female mice that were heat-stressed at 35°C for 10 h after hCG injection (oocyte maturation stage), or for 12 h on Day 1 of pregnancy (zygote stage), followed by in vitro culture. To minimize the effects of heat stress on the fertilization process, heat-stressed oocytes that were fertilized in vitro were also included in this experiment. In experiment 2, heat-stressed oocytes and zygotes were assayed for GSH content. The application of heat stress to the oocytes resulted in a significant decrease in the percentage of zygotes that developed to morulae or blastocysts, both for naturally fertilized oocytes (56.9% for heat-stressed vs 85.4% for control) or in vitro-fertilized oocytes (54.5%vs 73.6%). In the heat-stressed zygotes, the disruption of embryonic development was more drastic (24.3%vs 90.3%), with the majority of zygotes being arrested at the two-cell stage. In contrast, the GSH content decreased significantly in heat-stressed zygotes, but not in heat-stressed oocytes. These results demonstrate that the loss of developmental competence of early embryos is associated with a decrease in the GSH content of maternally heat-stressed zygotes, but not of maternally heat-stressed oocytes.
Document Type: Research Article
Affiliations: Institute of Agriculture and Forestry, University of Tsukuba, Tsukuba-shi, Japan
Publication date: April 1, 2004