Coordinate control of Na,K-ATPase mRNA expression by aldosterone, vasopressin and cell sodium delivery in the cortical collecting duct

We have examined the respective influence of aldosterone, vasopressin and c ell sodium delivery on Na+,K+-ATPase expression. The level of expression of the mRNA encoding for the alpha1- and beta1-subunits of Na+,K+-ATPase was evaluated in cortical collecting duct (CCD) cells from rats under different aldosterone status, in cells from the rat CCD cell line RCCD1 treated or n ot with vasopressin and in CCD cells from mice inactivated or not for the a lpha -subunit of the epithelial sodium channel. The amount of mRNA was dete rmined by in situ hybridization. Both aldosterone and vasopressin up-regula te transcripts encoding for the alpha1-subunit of Na+,K+-ATPase while beta1 is unaltered. Interestingly, when cell sodium entry was largely reduced (a lpha ENaC knock-out mice), the amount of transcripts encoding for the alpha 1-subunit of Na+,K-ATPase was significantly decreased in spite of high plas ma aldosterone concentrations. No effect was observed on beta1-subunit. Alt ogether, these results suggest a coordinated hormonal and ionic control of Na+,K+-ATPase expression by different transcriptional pathways (steroid-rec eptor, cAMP-dependent and Na+-dependent) in CCD cells. These regulations af fect only alpha1-subunit of Na+,K+-ATPase but not beta1.