Aldosterone Induces a Rapid Increase in the Rate of Na,K-ATPase Gene Transcription in Cultured Kidney Cells

Aldosterone (300 nM) induces a 4-fold increase over a 6-hr stimulation in A6 kidney cells from Xenopus laevis in the abundance of mRNA beta 1 and a 2-fold in that of mRNA alpha 1 coding for each Na,K-ATPase subunit, which is in agreement with a previous report. After a 3-hr stimulation already, aldosterone elicited a significant increase of mRNA beta 1 (2.51-fold +/- 0.47, n = 3, P less than 0.05) and a nonsignificant increase of mRNA alpha 1 (1.26-fold +/- 0.30, n = 3, NS). Increasing doses of cycloheximide up to 3 micrograms ml-1 led to 90% inhibition of protein synthesis, but failed to block the differential effect of aldosterone on mRNA abundance over a 6-h incubation period. The rate of transcription was measured by a nuclear run-on assay. The basal rate of mRNA alpha 1 transcription exceeded that of mRNA beta 1 by 2.8-fold. Aldosterone (300 nM) stimulated the transcription of the two subunit genes. Fifteen minutes after aldosterone addition there was a significant and parallel increase in the rate of transcription of the alpha 1 subunit (1.98-fold +/- 0.20, n = 3, P less than 0.02) and that of the beta 1 subunit (2.13 +/- 0.32, n = 3, P less than 0.04). After a 45-min stimulation period the transcription rate of the alpha 1 subunit remained at the level observed at 15 min (1.84-fold +/- 0.14, n = 4, P less than 0.01), while the transcription rate of the beta 1 subunit increased further (2.89-fold +/- 0.38, n = 4, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)