The interface of aging and salt in driving salt-sensitive hypertension: a comparative study in aged and young rats

Fig. 1. Effects of high salt diet on blood pressure in both aged and young DSS or SS.13BN rats (8 weeks or 50 weeks). MAP (a) and SBP (b) of aged rats; MAP (c) and SBP (d) of young rats; MAP (e) and SBP (f) of young and aged DSS rats. The values on the right side of the images were the absolute values between the two groups. Linear regression fitting of MAP (g) or SBP (h) in SS-HS-Y, SS-HS-O, SS.13BN-HS-Y, and SS.13BN-HS-O groups, and the linear fit equations are shown below the corresponding figures. SS-HS-Y and represents young DSS rats on high salt diet; SS-HS-O represents age DSS rats on high salt diet; SS.13BN-HS-Y represents young SS.13BN rats on high salt diet; SS.13BN-HS-O represents aged SS.13BN rats on high salt diet. Data are shown as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, * respected SS-NS vs SS-HS group; # p < 0.05, ## p < 0.01, # was SS.13BN-HS vs SS.13BN-NS; & p < 0.05, & & p < 0.01, & respected SS-HS-Y vs SS-HS-O group.

Fig. 2. Effect of high salt diet on cardiac function in rats. Ultrasound images of the SS-NS group in aged (a) and young (b) DSS rats, 1 shows left ventricular end-diastolic diameter (LVD), 2 shows left ventricular end-systolic diameter (LVS), 3 shows left ventricular septal thickness, and 4 shows heart rate (HR); LVFS (c), LVEF (d), SV (e), HR (f), CO (g) in aged and young rats; h the increase in SV and CO after high salt diet in young or aged DSS rats, HS-NS-O represents the SS-HS group minus SS-NS group in aged DSS rats, while HS-NS-Y represents the SS-HS group minus SS-NS group in young DSS rats. Data are shown as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.

Fig. 3. Changes of redox system in serum after high salt diet in aged and young rats. Serum concentrations of H2O2 (a), MDA (b), and NO (c) in aged and young rats. Data are shown as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.

Fig. 4. Effects of high salt on the abdominal aorta and femoral artery of rats. a The color Doppler image of the abdominal aorta in young DSS rats, peak systolic velocity (PS) represents the maximum blood flow rate during systole, while end-diastolic velocity (ED) represents the minimum blood flow rate during diastole. Time average maximum velocity (TAMAX) is the average of the maximum velocity in the cardiac cycle; b the inner diameter of the abdominal aorta in aged and young rats; PI of the abdominal aorta (c) or femoral artery (f) in aged and young rats; RI of the abdominal aorta (d) or femoral artery (g) in aged and young rats; S/D of the abdominal aorta (e) or femoral artery (h) in aged and young rats. Data are shown as Mean ± SD (n = 6). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.

Fig. 5. Changes in oxidative stress in the kidneys of aged and young rats after high salt diet. The levels of H2O2 in the cortex a and medulla b in aged and young rats; MDA levels in the cortex c and medulla d in aged and young rats; ROS in the kidneys of aged rats (e) and young rats (f), with red indicating positive staining. O-SS represents aged DSS rats, O-SS.13BN rats represent aged SS.13BN rats, NS stands for normal salt diet, and HS stands for high salt diet. 4 sections per group, with 15 fields of view per section, were analyzed under 20X objective lens; g the percentage of positive area of ROS in the kidneys of aged and young rats. Data are shown as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.

Fig. 6. Changes in the antioxidant system of the kidneys after high salt diet in aged and young rats. CAT activities in the renal cortex a and medulla b in aged and young rats; SOD activities in the renal cortex c and medulla d in aged and young rats; GSH-PX activities in the renal cortex e and medulla f in aged and young rats; expression of CAT in the renal cortex g and medulla h in young rats; CAT expression in the cortex i and medulla j of aged and young DSS rats; T-GSH concentrations in the renal cortex k and medulla l in aged and young rats; GSH concentrations in the renal cortex m and medulla n in aged and young rats; GSH/GSSG ratio in the renal cortex o and medulla p in aged and young rats. Data are shown as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.

Fig. 7. Effect of high salt diet on NO metabolism in aged and young rats. Renal NO in the cortex a or medulla b in aged and young rats; arginine concentrations in the cortex c or medulla d in aged and young rats; NOS activities in the cortex e or medulla f in aged and young rats; eNOS expression in the cortex g and medulla h of young rats, eNOS expression in the cortex i and medulla j of aged and young DSS rats. Data are presented as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.

Fig. 8. Changes in renal function after high salt diet in aged and young DSS or SS.13BN rats. Serum BUN a and creatinine b contents in aged and young rats; the UPC ratio in aged and young rats (c); Sirius Red and PAS staining of kidney in aged rats d or young rats (e), dark purple in PAS and red in Sirius Red staining was positive, 4 sections per group and 15 fields of view per section were counted under 20X objective lens; statistical analysis of the positive area of PAS (f) and Sirius Red (g) staining in the kidney of aged and young rats; h the positive area of PAS or Sirius Red staining in HS-SS group subtracted that of NS-SS group for young and aged DSS rats, HS-NS-O represented the SS-HS group minus SS-NS group in aged DSS rats, HS-NS-Y represented the SS-HS group minus SS-NS group in young DSS rats. Data are shown as Mean ± SD (n = 6–9). *p < 0.05, **p < 0.01, # p < 0.05, ## p < 0.01.