Van Winkle L J
J Exp Zool. 1981 Nov;218(2):239-46. doi: 10.1002/jez.1402180216.
Delayed implantation blastocysts remained in a diapausing-like state when incubated in Na+ -depleted (55 mM) medium. Accumulation of radioactive amino acids remained low when embryos were in low Na+ medium, but increased in the manner characteristic of these embryos when placed in high (124 mM) Na+ medium. Differentiation of blastocysts was apparently arrested in medium containing only 55 mM Na+ since no progress toward formation of trophoblastic outgrowths was made in this medium even when it contained all other compounds required for this process. Low Na+ may prevent uptake of amino acids, such as lysine, essential to outgrowth formation. Accumulation of lysine was Na+ -dependent in blastocysts even though this amino acid is not transported via a Na+-symport system in most cell types. Glucose deprivation did not affect the increase in the capacity of delayed implantation blastocysts to take up amino acids when incubated in high Na+ medium, and glucose accumulation was not Na+-dependent. The capacity of delayed implantation blastocysts to take up amino acids was inversely related to the time before these embryos began forming outgrowths in vitro. The latter process occurred more rapidly if diapausing blastocysts had been stimulated in utero by injecting overiectomized mice with progesterone and estrogen. However, these hormones slowed outgrowth formation slightly when present in the culture medium in vitro.
当在低钠（55 mM）培养基中培养时，延迟着床的囊胚处于类似滞育的状态。当胚胎处于低钠培养基中时，放射性氨基酸的积累仍然很低，但当置于高钠（124 mM）培养基中时，其积累以这些胚胎特有的方式增加。囊胚的分化显然在仅含55 mM钠的培养基中被阻止，因为即使该培养基含有此过程所需的所有其他化合物，在该培养基中也没有向滋养层外突形成的方向发展。低钠可能会阻止对滋养层外突形成至关重要的氨基酸（如赖氨酸）的摄取。即使在大多数细胞类型中这种氨基酸不是通过钠协同转运系统运输的，但囊胚中赖氨酸的积累是依赖钠的。当在高钠培养基中培养时，葡萄糖剥夺并不影响延迟着床囊胚摄取氨基酸能力的增加，并且葡萄糖的积累不依赖钠。延迟着床囊胚摄取氨基酸的能力与这些胚胎在体外开始形成外突之前的时间呈负相关。如果通过给去卵巢小鼠注射孕酮和雌激素在子宫内刺激滞育囊胚，后一过程会更快发生。然而，当这些激素存在于体外培养基中时，它们会稍微减缓外突的形成。
