STC-l is expressed in kidney collecting duct cells and targeted to most other nephron segments. However, its function and regulation are both unclear. The present study explored the regulation of Stc-1 mRNA levels in vivo in rat models of dehydration and overhydration. Dehydration caused an upregulation in Stc-1 mRNA levels in kidney cortex and to a lesser extent the inner medulla. Antidiuretic hormone was identified as a potential mediator of gene induction during dehydration acting through the V2 receptor. In contrast overhydration did not produce changes in renal gene activity. Histological studies revealed no difference in STC-1 receptor distribution along the nephron indicative of similar targeting pathways irrespective of hydration states. Together the findings are suggestive of a novel role for renal STC-1 in the regulation of extracellular fluid volume, in particular during water deprivation
