The effect of cryopreservation on the metabolic activity of day-6.5 horse embryos.

This research studies the impact of cryopreservation on the metabolic activity of horse embryos, suggesting that it may inhibit anaerobic glucose metabolism while stimulating aerobic glutamine metabolism, with the cryoprotectant being the cause, rather than freezing and thawing processes.

Introduction and Methodology

• The research explored the hypothesis that the decrease in the viability of embryos due to cryopreservation may be partly attributed to metabolic disturbances.
• Day -6.5 horse embryos were used for this experiment and they were subjected to three different conditions: being frozen and thawed using glycerol as the cryoprotectant, given only the glycerol treatment or washed an equal number of times in phosphate-buffered saline (PBS).
• The embryos were incubated with L-[14C(U)]-glutamine and D-[5-3H]-glucose to measure Krebs cycle activity (a part of cellular respiration) and Embden-Meyerhof pathway activity (anaerobic glucose metabolism), respectively, both before and after the treatment.

Results and Interpretation

• Before the experiment, glucose metabolism and glutamine metabolism varied considerably, but both were highly related to the volume of the embryo.
• Post treatment, the control group showed a 76% increase in glucose metabolism, with only a 1% increase for the treated groups. On the contrary, glutamine metabolism exhibited only a 10% increase in the control situation but a 50% increase in the treated embryos.
• There was no alteration in the mean ratio of glucose to glutamine metabolism before treatment between groups. However, this ratio almost doubled in the control group as opposed to the treated group after treatment.
• The data thus produced indicates cryopreservation has an inhibitory effect on anaerobic glucose metabolism and a stimulatory effect on aerobic glutamine metabolism.
• However, crucially, the research discovered that such effects are attributed to the glycerol-based cryoprotectant used in the process, and not specifically due to the freezing and thawing integral to cryopreservation.