NKCC2 is the kidney-specific Na-K-Cl cotransporter responsible for Na reabsorption in the thick ascending Henle's loop (TAHL). Its activity is required to dilute the urine and to concentrate the medullary interstitium. NKCC2 is regulated by phosphorylation, through a pathway involving Pask/OxSR1 and WNK family of kinases. Recently, AMP-activated kinase (AMPK) has been involved in modulating NKCC2 activity in the TAHL. AMPK is expressed in the apical compartment of TAHL cells, its activity being modulated in vivo by dietary salt. AMPK and NKCC2 co-immunoprecipitate when expressed in the same cells and in vivo. It has been shown in vitro that AMPK do phosphorylate NKCC2, using Ser126 as substrate. A Ser126Ala mutant NKCC2 shows impaired regulatory properties. We are studying the renal phenotype in two lines of mice with genetic deletion of AMPK, one for either isoform of the catalytic alpha subunit. Our results show only minor differences in alpha-KO mice compared to wild-type mice. Alpha-1 KO mice excrete less volume of a concentrated urine, but there are no differences in their response to Na⁺ challenges. Alpha-2 KO mice, on the other hand, tend to excrete a higher volume of a diluted urine, specially when placed under Na⁺ restriction. Deletion of alpha-2 has no effects on NKCC2 expression or activity; however, alpha-1 KO mice do show a marked increase in NKCC2 expression, while its phosphorylation is reduced. The mild consequences of alpha-1 deletion might be neutralized by an observed upregulation in alpha-2 expression or other unexplored compensatory mechanisms.