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Regulation of amino acid transport in chicken embryo fibroblasts by purified multiplication‐stimulating activity (MSA)
Author(s) -
Derr James T.,
Smith Gary L.
Publication year - 1980
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041020109
Subject(s) - embryo , amino acid , stimulation , biochemistry , dna synthesis , biology , mitosis , rna , microbiology and biotechnology , chemistry , dna , endocrinology , gene
Enhanced amino acid transport is observed when quiescent cultures of chicken embryo fibroblasts are stimulated to proliferate by the addition of purified multiplication‐stimulating activity (MSA). This increase in amino acid transport is an early event occuring prior to the onset of DNA synthesis in stimulated cells. Results indicate that the changes in transport activity, as measured by α‐aminoisobutyric acid (AIB) uptake, are due to stimulation of only the Na + ‐dependent A transport system. There is little or no change in the activities of transport systems ASC, L, or Ly + upon exposure to MSA. A kinetic analysis shows this increased activity is due to a change in Vmax while K m remains unaltered. Continuous exposure to the stimulus is required to maintain the increased level of transport activity and the presence of inhibitors of RNA and protein synthesis significantly inhibits the response. Results also indicate that a similar specific increase in the A transport system is initiated when RSV tsNY68 infected cells are shifted to the permissive temperature. It appears that the A system of mediation is emerging as a strategic regulatory site for cell function.