I013 Effects of high salt diet on mechanical properties of the middle cerebral artery

Abstract

A high salt diet (HSD) is a risk factor for stroke. However, little is known about the consequences of a HSD on the mechanical properties of cerebral vessels. The aim of the present work was to evaluate the impact of a HSD on the distensibility of the middle cerebral artery (MCA). Normotensive male Wistar rats were given a normal diet (n=11) or HSD (n=10; 1 % NaCl in drinking water) for 1 month. Sodium balance was calculated as the difference between sodium intake and sodium excretion. MCA were mounted and pressurized (60 mmHg, i.e. 60 % of mean blood pressure, BP) in a small vessel arteriograph. Passive (inactivation of smooth muscle cells, EDTA 2 mM) internal diameter (ID) and wall thickness (WT) of MCA were measured during a stepwise increase in intraluminal pressure (IP, 20 to 160 mmHg, 20 mmHg per step). Stress (σ = ID × IP / 2WT) and strain (ɛ = (ID-ID0) / ID0 where ID0 is ID at 20 mmHg) were calculated. Stress—strain data were fitted to an exponential curve σ =σ0.e(ET.ɛ), where σ0 is the stress at 20 mmHg and ET is the slope of the tangential elastic modulus versus stress . HSD produced a positive sodium balance (5±1 mEq/24h/kg, P<0.05 versus -1±1 in controls) but did not modify BP (110±6 mmHg, 109±4 in controls rats). The stress-strain curve was shifted to the left in rats with a HSD (ET: 8.1±0.8, P<0.05 versus 5.8±0.4 in controls). In conclusion, a HSD induces an increase in wall stiffness of the MCA in the absence of any effect on BP. This may (partially) contribute to the cerebrovascular dysfunction linked to stroke in patients on a HSD.