Aortic wall composition and mechanical properties vary along the arterial tree. The distensibility of the thoracic aorta (TA) has the capacity to accommodate high pulsatile pressure during cardiac systole whereas the abdominal aorta (AA) is less distensible. This regional variation may be altered in conditions where stiffening occurs, such as aging, hypertension and kidney disease, further compromising blood pressure regulation and increasing risk of end organ damage. The aim of this study was to determine regional variation of aortic biomechanical properties in a rat model of chronic kidney disease with associated hypertension, comparing the Lewis Polycystic Kidney rat (LPK) to Lewis controls. Unbranched, 2–4 mm long descending TA rings and AA rings (distal to the renal bifurcations) were obtained from animals aged 12–13 weeks (n26). Aortic rings were assessed in vitro using a uniaxial tensile test in which aortic segments were stretched at 2 mm/min until breaking point. Results were determined by calculating stress and strain at break, thereby providing measures of the elastin modulus (EM), collagen modulus (CM) and the area under the stress-strain curve which represents the energy absorbed (EA) by the sample. Strain at break did not differ between TA and AA of LPKs but did differ in Lewis controls (44±2 vs 55±4 %, P<0.02), leading to a lower magnitude of change in strain between TA and AA in LPK relative to Lewis (-8±3 vs 11±4 %, P<0.005). A greater stress at break was observed for AA compared to TA for both groups (both P<0.0001) but the magnitude did not differ between the two strains. AA had higher EM compared to TA in LPKs only (0.8±0.1 vs 0.4±0.02 MPa, P<0.0001), resulting in a greater change in EM between TA and AA in LPK compared to Lewis (0.4±0.1 vs 0.1±0.1 MPa, P<0.007). CM and EA values for AA were higher than TA in both experimental groups but there was no significant difference in magnitude between the strains. These results suggest that LPKs have a higher gradient of stiffness along the descending aorta, which may alter the characteristics of flow in the vessel and contribute to the increased pulse pressures and hypertension seen in these animals.
|Number of pages
|Published - Aug 2012
|33rd Annual Scientific Meeting of the High-Blood-Pressure-Research-Council-of-Australia (HBPRCA) - Perth, Australia
Duration: 6 Dec 2011 → 9 Dec 2011