Decreased renal Na-K-2Cl cotransporter abundance in mice with heterozygousdisruption of the G(s)alpha gene

Transport processes along the nephron are regulated in part by hormone stim ulation of adenylyl cyclases mediated by the heterotrimeric G protein G(s). To assess the role of this pathway in the regulation of Na-K-2Cl cotranspo rter abundance in the renal thick ascending limb (TAL), we studied mice wit h heterozygous disruption of the Gnas gene, which codes for the alpha-subun it of G(s). Outer medullary G(s)alpha protein abundance (as assessed by sem iquantitative immunoblotting) and glucagon-stimulated cAMP production were significantly reduced in the heterozygous G(s)alpha knockout mice (GSKO) re lative to their wild-type (WT) littermates. Furthermore, Na-K-2Cl cotranspo rter protein abundance in the outer medulla was significantly reduced (band density, 48% of WT). In addition, GSKO mice had a significantly reduced (7 2% of WT) urinary osmolality in response to a single injection of 1-deamino -[8-D-arginine]vasopressin (DDAVP), a vasopressin analog. In contrast, oute r 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 litterm ates. However, abundance of type VI adenylyl cyclase was markedly decreased in the outer medullas of GSKO mice, suggesting a novel feed-forward regula tory mechanism. We conclude that expression of the Na-K-2Cl cotransporter o f the TAL is dependent on G(s)alpha-mediated hormone stimulation, most like ly due to long-term changes in cellular cAMP levels.