Assessment of functional integrity of frozen–thawed mouse embryos by albumin and leucine uptake

Abstract

To assess the effects of freezing-thawing on metabolic functions of embryos prior to implantation, we measured the uptake of [125I]bovine serum albumin (BSA) and [3H]leucine in 2-cell mouse embryos, that were freshly collected (control), exposed to cryoprotectants (non-frozen), and frozen-thawed, and in morulae and blastocysts cultured from these 2-cell embryos. No significant difference in [125I]BSA uptake by 2-cell embryos was observed among the three groups. However, [125I]BSA uptake by blastocysts in the frozen-thawed group was significantly reduced compared with the control and non-frozen groups. [3H]leucine uptake by 2-cell embryos in the frozen-thawed and non-frozen groups was significantly less than in the control group. Fluorescein diacetate staining was performed in the control and frozen-thawed 2-cell embryos. The intensity of fluorescence after fluorescein diacetate exposure did not differ between the control and frozen-thawed embryos. The present study with mouse embryos suggests that freezing-thawing procedures impair the metabolic functions, in particular the membrane transport system, of embryos. Measurements of BSA and leucine uptake in embryos may be useful for evaluating the quality of frozen-thawed embryos.