A novel mechanism contributing to development of Dahl salt-sensitive hypertension: role of the transient receptor potential vanilloid type 1.

To determine the role of the transient receptor potential vanilloid type 1 (TRPV1) channels in development of hypertension in Dahl salt-sensitive (DS) rats fed a high-salt diet (HS), male DS and Dahl salt-resistant (DR) rats were maintained on a low-salt diet (LS) or HS for 3 weeks. HS significantly increased systolic blood pressure in DS+HS rats compared with DS+LS, DR+HS, and DR+LS rats. Intravenous bolus injection of capsazepine (3 mg/kg), a selective TRPV1 antagonist, significantly increased mean arterial pressure in conscious DR+HS rats compared with DR+LS, DS+/-HS, and DS+/-LS rats. In contrast, capsaicin (10 or 30 microg/kg), a selective TRPV1 agonist, dose-dependently decreased mean arterial pressure in all of the groups with the most profound magnitude in DR+HS rats compared with the other 3 groups. TRPV1 expression in mesenteric resistance arteries and the renal cortex and medulla, calcitonin gene-related peptide levels in dorsal root ganglia, and calcitonin gene-related peptide-positive sensory nerve density in mesenteric resistance arteries were significantly decreased in DS+HS rats compared with DS+LS, DR+HS, and DR+LS rats. Taken together, our data indicate that the TRPV1 receptor is activated and its expression upregulated during HS intake in DR rats, which acts to prevent salt-induced increases in blood pressure. In contrast, TRPV1 expression and function are impaired in DS rats, which renders DS rats sensitive to salt load in terms of blood pressure regulation.