A total of seven-week-old male SHR and Wistar Kyoto rats (WKY) weighing 200-250 g were obtained from Shanghai Laboratory Animal Center of the Chinese Academy of Science (Shanghai, China), and received humane care in compliance with the Guide for the Care and Use of Laboratory Animals (NIH Pub. no. 85-23, revised 1996), which was approved by the Institutional Ethics Review Board of the Characteristic Medical Center of the Chinese People's Armed Police Forces (Tianjin, China; approval number: 2012-0005). Rats were maintained in a 12/12-h dark/light cycle in air-conditioned rooms (23±1˚C, 55±5% humidity) and were acclimated to the local conditions for 1 week before the study. At 8 weeks of age, rats were divided randomly (n=12 for each group), and then given either a low-salt (LS; 0.5% NaCl) or HS diet (8% NaCl) for 8, 12 or 16 weeks. All rats were permitted free access to chow and tap water.