ISSN:
1432-1424
Keywords:
Na,K-ATPase gene transcription
;
Cell Na+ and K+
;
Na+-free medium
;
Na+ entry
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract The role of enhanced Na+ entry in the induction of Na,K-ATPase subunit mRNAs by serum was investigated in a “nontransformed” rat liver cell line, Clone 9. Exposure of cells to 10% calf serum resulted in a 1.5-fold increase in the rate of Na+ entry associated with a transient rise in cell Na+ content (twofold at 15 min) and a sustained 1.15-fold rise in cell K+ content. After 6 hr of exposure to serum mRNAα1 and mRNAβ1 content increased by 1.8 and 2.6-fold, respectively. In nuclear run-on assays, serum stimulated the transcription of the α1 gene ∼ 1.9-fold while the transcription rate of the β1 gene remained unchanged. In cells incubated in Na+-free medium where NaCl was replaced by choline chloride, the induction of mRNAα1 by serum was fully preserved, whereas the increase in mRNAβ1 was prevented. An unexpected finding was that incubation of cells in Na+-free medium alone for 6 hr increased mRNAα1 but not mRNAβ1 content. These results indicate that Na,K-ATPase subunit mRNAs are differentially induced by serum, and that the induction of mRNAα1, in contrast to that of mRNAβ1, is transcriptionally mediated and does not require the presence of Na+ in the extracellular medium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00234994
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