Decreased renal Na-K-2Cl cotransporter abundance in mice with heterozygous disruption of the Gsα gene.

Transport processes along the nephron are regulated in part by hormone stimulation of adenylyl cyclases mediated by the heterotrimeric G protein Gs. To assess the role of this pathway in the regulation of Na-K-2Cl cotransporter abundance in the renal thick ascending limb (TAL), we studied mice with heterozygous disruption of the G nas gene, which codes for the α-subunit of Gs. Outer medullary Gsα protein abundance (as assessed by semiquantitative immunoblotting) and glucagon-stimulated cAMP production were significantly reduced in the heterozygous Gsα knockout mice (GSKO) relative to their wild-type (WT) littermates. Furthermore, Na-K-2Cl cotransporter protein abundance in the outer medulla was significantly reduced (band density, 48% of WT). In addition, GSKO mice had a significantly reduced (72% of WT) urinary osmolality in response to a single injection of 1-deamino-[8-d-arginine]vasopressin (DDAVP), a vasopressin analog. In contrast, outer medullary protein expression of the type 3 Na/H exchanger (NHE-3) or Tamm-Horsfall protein did not differ between the GSKO mice and their WT littermates. However, abundance of type VI adenylyl cyclase was markedly decreased in the outer medullas of GSKO mice, suggesting a novel feed-forward regulatory mechanism. We conclude that expression of the Na-K-2Cl cotransporter of the TAL is dependent on Gsα-mediated hormone stimulation, most likely due to long-term changes in cellular cAMP levels.