Effect of Aging and Hypertension on Cerebral Artery Volume as Measured by MRI in Dahl‐Salt Sensitive Rats.
Authors: Naraine Akshay S. , McPherson Rebecca L. , Lee Diana , Rejimon Abinand , Fishbein Kenneth W. , Spencer Richard G. , Lakatta Edward G. , Fedorova Olga V. 
Published: June 2021

Aging and hypertension lead to the structural changes in the cerebral vasculature, especially in basilar artery (BA). The BA supplies oxygenated blood to brain tissues and to the circle of Willis. Impairment in endothelial dilation of the BA occurs during hypertension, however, arterial volume changes of the BA during age‐associated hypertension are not fully understood. We employ MRI to examine age‐dependent volumetric and length changes in the BA in the Dahl‐salt sensitive rats (Dahl‐S), which develops hypertension during aging on a normal salt intake, unlike the Sprague‐Dawley rats (SD), from which the Dahl‐S strain was derived.

Hypothesis

Arterial volume changes in the BA are associated with hypertension and aging in Dahl‐S compared to SD.

Methods

Using a 7 Tesla 30 cm Bruker Biospec scanner, time‐of‐flight (TOF) 3D MRI scans were obtained in SD and Dahl‐S male rats on normal 0.5% NaCl intake at age 3 (n=5/7), 6 (n=16/8), and 12‐mo (n=9/5; SD/Dahl‐S) to visualize blood flow within the BA. The BA was manually segmented using AMIRA, and the length was also measured. The BA was segmented from the vertebral arteries to the rostral cerebellar arteries. Total BA volume was normalized to BA length. Systolic blood pressure (SBP) was recorded using tail cuff plethysmography prior to MRI at each time point. Data were analyzed by 2‐way ANOVA with a Tukey's posthoc test. The data are presented as mean ± standard deviation.

Results

SD and Dahl‐S had comparable SBP at 3‐mo (131±7 vs. 140±13 mmHg; p>0.05), but Dahl‐S exhibited significant SBP increase with aging vs. SD from 3 to 6‐mo (p<0.001) with a strain difference at 6 and 12‐mo ages (Dahl‐S: 167±17 mmHg vs. SD: 130±11 mmHg at 6‐mo, and Dahl‐S: 169±13 mmHg vs. SD: 141±9 mmHg at 12‐mo, p<0.001). In Dahl‐S, BA volume increased from 3 to 6‐mo (1.13±0.17 to 2.31±0.24 mm3, p<0.001) then decreased from 6 to 12‐mo (2.31±0.24 to 1.13±0.15 mm3, p<0.001). BA volume in SD rats exhibited a similar trend by increasing from 3 to 6‐mo (2.79±0.47 mm3 to 4.19±0.71 mm3, p<0.001) then decreasing from 6 to 12‐mo (4.19 mm3 ± 0.71 to 2.50±0.22 mm3, p<0.001). SD had a greater BA volume at all three timepoints with respect to age‐matched Dahl‐S (p<0.001). Additionally, Dahl‐S showed a greater percent change in BA volume from 3 to 6‐mo compared to SD (105% vs. 50%, Dahl‐S vs. SD, respectively), and from 3 to 12‐mo (0% vs. −10%, Dahl‐S vs. SD, respectively), i.e., Dahl‐S went back to baseline, while SD showed a decrease in BA volume. Our previous results have demonstrated that Dahl‐S have a 10% smaller total brain volume compared to SD which may contribute to some of the strain differences in BA volume.

Conclusion

The time between age 3 and 6‐mo appears to be a pivotal time for changes in the cerebral arteries demonstrated by increase in BA volume in Dahl‐S and SD, and this increase was more pronounced in Dahl‐S. Decrease in BA volume in Dahl‐S along with higher blood pressure with an advancing age may indicate an increased vulnerability of cerebral arteries and susceptibility in rat model of age‐dependent hypertension.

Support or Funding Information

This work was supported by NIH/NIA Intramural Research Program.

This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.