Vitrification of hamster 2-cell embryos impairs the activity of both the Na
+/H+ antiporter and HCO3-/Cl- exchanger; the two transport proteins respons
ible for the regulation of intracellular pH (pHi). The activities of both t
he Na+/H+ antiporter and HCO3-/Cl- exchanger were significantly reduced at
4 h following warming compared to freshly collected embryos. Normal levels
of activity of both transporters were not restored until 6 h after warming.
Thus, cryopreservation of cleavage stage hamster embryos has a detrimental
effect on their ability to maintain intracellular ionic homeostasis. Impai
rment of these pHi regulatory proteins resulted in the pHi of embryos being
significantly elevated from the control values of 1.2 to 7.35 for approxim
ately 4 h after warming. In addition, an elevated pHi value significantly i
mpaired oxidative metabolism. Therefore, the loss in developmental competen
ce of embryos following cryopreservation mag in part be explained by a redu
ced ability to regulate intracellular pH that results in perturbations in m
etabolism and disruption of energy production.