We have previously shown that renal sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite formed by phosphorylation of sphingosine, increases sodium excretion through inhibition of epithelial sodium channel (ENaC) via S1P receptor 1, which is mainly localized in the collecting ducts. However, the role of S1P-producing enzyme in renal sodium excretion remains unknown. The immediate substrate for S1P generation, sphingosine, is formed from the hydrolysis of ceramide by ceramidase, which is a rate-limiting step for S1P production. Acid ceramidase (AC) is the major form of ceramidase in collecting duct. The present study was to test the hypothesis that deletion of AC in the collecting ducts impacts renal sodium handling. Mice with collecting duct-specific AC knockout (CD-AC-KO) were generated by crossing AC floxed mice with Aquoporin 2-Cre mice. The specific knockout of AC in renal collecting ducts was confirmed by immunohistochemistry and Western blot analyses. Functionally, urinary sodium excretion was decreased by 40% in CD-AC-KO mice compared with control mice (Ctrl) after acute IV sodium loading (2.19±0.32 vs. 1.3±0.18 μmole/min.g kwt in Ctrl vs. KO, P<0.05). Furthermore, the natriuretic response to elevated renal perfusion pressure (pressure natriuresis) was severely impaired in CD-AD-KO mice compared with control mice (5.3±0.54 vs. 3.0±0.25 μmole/min.g kwt in Ctrl vs. KO, P<0.05). Moreover, chronic high salt-induced sodium retention was remarkably enhanced in CD-AC-KO mice compared with control animals (2.9±0.21 vs. 5.0±0.30 mmole/100g bw. 24h in Ctrl vs. KO, P<0.05). These results suggest that AC in renal collecting ducts plays an important role in the regulation of renal sodium excretion and that modulation of AC function in the kidneys could be a therapeutic approach for salt-sensitive hypertension.