Changes in the activities of amino acid transport systems b0,+ and L during development of preimplantation mouse conceptuses
| Autor: | L J Van Winkle, Allan L. Campione, James M. Gorman, B D Weimer |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Arginine
Lysine Biophysics Biology Biochemistry Mice Leucine medicine Animals Blastocyst Amino Acids reproductive and urinary physiology Ovum chemistry.chemical_classification System L Leucine transport Sodium Biological Transport Cell Biology Amino acid medicine.anatomical_structure chemistry embryonic structures Lysine transport |
| Zdroj: | Biochimica et biophysica acta. 1021(1) |
| ISSN: | 0006-3002 |
| Popis: | Uptake of leucine, lysine, and arginine was predominantly Na(+)-independent in mouse conceptuses through the 8-cell stage of development, and two components of saturable transport were detected for each of these amino acids. Uptake of cationic substrates from solutions near 1 microM was inhibited most strongly by bulky cationic and zwitterionic amino acids whose carbon skeletons do not branch at the alpha or beta positions. By this criterion, system b0,+ accounted for most of the Na(+)-independent arginine and lysine transport in eggs and conceptuses throughout preimplantation development. A small, leucine-resistant, cation-preferring component of amino acid transport was also detected in these cells. Leucine uptake was inhibited most strongly by bicyclic, branched-chain or benzenoid, zwitterionic amino acids in eggs and conceptuses prior to formation of blastocysts. Therefore, it appeared to be taken up mainly by system L, while system b0,+ accounted for a smaller portion of leucine uptake during this developmental period. In blastocysts, in contrast, system L was less conspicuous, and system b0,+ was primarily responsible for Na(+)-independent leucine uptake. The Vmax values for transport of amino acids by system b0,+ increased by up to 30-fold in conceptuses between the 1-cell and blastocyst stages. In contrast, the Vmax value for leucine transport via system L decreased while the Km value increased between these two developmental stages. Although several explanations for these changes are possible, we favor the hypothesis that the density of system L transport sites in plasma membranes decreases while the number of system b0,+ sites increases during development of blastocysts from 1-cell conceptuses. |
| Databáze: | OpenAIRE |
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