Renal sodium transport in renin-deficient Dahl salt-sensitive rats.

Objective: The Dahl salt-sensitive rat is a well-established model of salt-sensitive hypertension. The goal of this study was to assess the expression and activity of renal sodium channels and transporters in the renin-deficient salt-sensitive rat.

Methods: Renin knockout (Ren(-/-)) rats created on the salt-sensitive rat background were used to investigate the role of renin in the regulation of ion transport in salt-sensitive hypertension. Western blotting and patch-clamp analyses were utilized to assess the expression level and activity of Na(+) transporters.

Results: It has been described previously that Ren(-/-) rats exhibit severe kidney underdevelopment, polyuria, and lower body weight and blood pressure compared to their wild-type littermates. Here we found that renin deficiency led to decreased expression of sodium-hydrogen antiporter (NHE3), the Na(+)/H(+) exchanger involved in Na(+) absorption in the proximal tubules, but did not affect the expression of Na-K-Cl cotransporter (NKCC2), the main transporter in the loop of Henle. In the distal nephron, the expression of sodium chloride cotransporter (NCC) was lower in Ren(-/-) rats. Single-channel patch clamp analysis detected decreased ENaC activity in Ren(-/-) rats which was mediated via changes in the channel open probability.

Conclusion: These data illustrate that renin deficiency leads to significant dysregulation of ion transporters.