It has been indicated that non-dipper pattern of circadian rhythm of blood pressure (BP) is a great risk of cardiovascular disease, which is accompanied by impaired renal function and proteinuria. Here, we aimed to investigate the circadian rhythm of BP during the progression of renal injury in Dahl salt-sensitive (DSS) hypertensive rats.Design and Method:
DSS rats were treated with a high salt diet (HS; 8% NaCl) for 10 weeks (n = 10).Results:
Before starting a HS diet, the difference in mean arterial pressure (MAP) between dark and light period was 6.5 ± 0.6 mmHg in normal salt (0.3% NaCl)-fed DSS rats. Treatment with a HS diet for 5 days did not change renal function, but blood pressure was increased. Furthermore, the difference in MAP between dark and light period was significantly increased (11.1 ± 0.9 mmHg, P < 0.05), suggesting extreme dipping type of circadian BP. However, further HS diet feeding for 10 weeks induced the development of hypertension, renal tissue injury and proteinuria, which were associated with non-dipper pattern of BP. Namely, the MAP was similar between dark and light period (180 ± 6 vs.180 ± 6 mmHg). After switching to normal salt diet for 4 weeks, MAP was significantly decreased and circadian rhythm of BP was returned to normal dipper type (157 ± 4 vs. 150 ± 4 mmHg for MAP in dark and light period, respectively).Conclusions:
These data support the hypothesis that non-dipping pattern of BP is associated with the progression of renal injury during the development of salt-dependent hypertension, which may contribute to the cardiovascular events.