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>Amino acid transport in chick embryo fibroblasts: Evidence for transcriptional regulation of transport following serum addition
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Amino acid transport in chick embryo fibroblasts: Evidence for transcriptional regulation of transport following serum addition
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机译：Amino acid transport in chick embryo fibroblasts: Evidence for transcriptional regulation of transport following serum addition
AbstractChanges in amino acid transport activity by system A (a Na+‐dependent agency with affinity for a discrete group of neutral amino acids) caused by the addition of serum to serum‐deprived cultured chick embryo fibroblasts have been evaluated by measurements of14C‐labeled L‐proline and α‐methylaminoisobutyric acid uptake under conditions approaching initial entry rates. Dialysed serum was as effective as undialysed serum in stimulating amino acid transport. This effect was inhibited by 7 μM cycloheximide, by 80 nM actinomycin D and by 40 μM cordycepin, but not by 0.3 mM cytosine arabinoside. Cultured avian fibroblasts previously incubated in a cycloheximide‐containing medium (phase of inhibited translation) in the presence of serum, subsequently exhibited a net increase of proline transport activity when transferred to a medium containing actinomycin D (phase of inhibited transcription). Omission of serum in the cycloheximide‐phase prevented the increase of transport activity during subsequent incubation in the actinomycin D‐phase; omission of serum in the actinomycin D‐phase allowed a shorter and less pronounced increase of transport activity than in the presence of serum. Additions of actinomycin D or cycloheximide slightly increased the rate of decay of amino acid transport caused by serum withdrawal. These observations suggest that in cultured avian fibroblasts, serum modulates the activity of transport system A by a mechanism acting at the
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