Objective To evaluate the effect of 3 anti-hypertensive drugs on blood pressure (BP) and left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR) with cold stress.
Methods Forty male SHR were randomly divided into five groups (n = 8):control group (SHR-C), cold stress control group (C-SHR-C, in 5 ± 2°C walk-in chamber for 4 hours per day); and 3 treated cold groups:metoprolol (C-SHR-M, 50mg/kg.d), amlodipine (C-SHR-A, 2.5mg/kg.d), and benazepril (C-SHR-B, 10mg/kg.d). In the 6 week period, SBP, body weight (BW) and heart rate (HR) were measured once a week. At the sixth week, left ventricle weight (LVW) and LV weight index (LVWI), the concentrations of Endothelin-1 (ET-1) and nitric oxide (NO) in blood and myocardial, myocardial mRNA expression of ET-A receptor (ETAR mRNA) were gained.
Results One week cold stress increased significantly SBP in SHR. The SBPs in the 3 intervention groups were lower than in C-SHR-C from the 3rd week, especially in amlodipine group. Their LVWI, ET-I levels in blood and myocardium and the expression of ETAR mRNA were lower and the NO were higher, but the best effect was seen in the amlodipine group.
Conclusions Cold stress can induce significant SBP and LVWI increase in SHR, and ET system activation is a responsive factor for LVH. On the usually recommended doses, amlodipine offered better effect on SBP control and LVH prevention than metoprolol and benazepril.