Mean arterial pressure (MAP) during the active and dormant phases in salt-sensitive (SS) and salt-resistant (SR) rats as a function of age and ovariectomy. After being weaned, all rats were maintained on a low-sodium diet (<0.13% NaCl). Ovariectomies or sham surgeries were conducted at 3 mo. Shown is average MAP measured by radio telemetry in the active and dormant phases in SS (A–C) and SR (D and E) rats in SS intact (solid black bar) rats at 1 mo (A), in SS-SHAM (solid black bar) and SS-OVX (striped black bar) rats at 4 mo (B) and at 7 mo (C), and in SR-SHAM (solid white bar) and SR-OVX (striped white bar) rats at 4 mo (D) and 7 mo (E); $P < 0.0001 vs. active phase; SS/JrHsd/Env, salt-sensitive rats developed by John Rapp, distributed by Harlan, and purchased from Envigo; SR/JrHsd/Env, salt-resistant rats developed by John Rapp, distributed by Harlan, and purchased from Envigo; n, number of rats.