Prather R S, Peters M S, Van Winkle L J
Department of Animal Science, University of Missouri-Columbia 65211.
Mol Reprod Dev. 1993 Sep;36(1):49-52. doi: 10.1002/mrd.1080360108.
Amino acid transport is facilitated by specific transporters within the plasma membrane of the cell. Mediated Na(+)-independent transport of L-glutamate can be easily detected in mouse oocytes, but it is nearly undetectable in blastocyst-stage embryos. In contrast, the Na(+)-dependent transport of L-aspartate is not detectable in oocytes, but it is detectable in eight-cell embryos and reaches relatively high levels by the blastocyst stage. It is believed that the amino acid transporters responsible are systems x-c and X-AG, respectively. Here we report the detection of Na(+)-dependent L-aspartate transport, which increased as pig blastocysts developed, although Na(+)-dependent aspartate transport was not detected in pig oocytes. Mediated Na(+)-independent L-glutamate transport was not detected in pig oocytes, in contrast to the mouse, nor in early or hatched pig blastocysts. Thus, while the developmental regulation of system X-AG is similar in both the pig and the mouse, system x-c was not detectable in pig oocytes or blastocysts. Elucidation of the molecular mechanisms controlling amino acid transport and other gene expression in early embryos should contribute to an understanding of whether and even why some aspects of developmental regulation of gene expression may need to differ among species.
氨基酸转运由细胞的质膜内特定的转运蛋白促进。在小鼠卵母细胞中可以很容易地检测到介导的L-谷氨酸的Na⁺非依赖性转运，但在囊胚期胚胎中几乎检测不到。相反，L-天冬氨酸的Na⁺依赖性转运在卵母细胞中检测不到，但在八细胞胚胎中可检测到，到囊胚期达到相对较高水平。据信负责的氨基酸转运蛋白分别是系统x-c和X-AG。在这里我们报告检测到Na⁺依赖性L-天冬氨酸转运，其随着猪囊胚的发育而增加，尽管在猪卵母细胞中未检测到Na⁺依赖性天冬氨酸转运。与小鼠不同，在猪卵母细胞中未检测到介导的Na⁺非依赖性L-谷氨酸转运，在早期或孵化后的猪囊胚中也未检测到。因此，虽然X-AG系统的发育调控在猪和小鼠中相似，但在猪卵母细胞或囊胚中未检测到系统x-c。阐明控制早期胚胎中氨基酸转运和其他基因表达的分子机制，应该有助于理解在物种间基因表达的发育调控的某些方面是否甚至为何可能需要有所不同。
