P4.16 EFFECT OF DENERVATION ON VISCOELASTIC PROPERTIES OF LARGE ARTERIES IN POLYCYSTIC KIDNEY DISEASE RATS

Abstract

Objectives: Arterial elasticity is determined by passive mechanical properties of wall components modulated by neurogenic effects on smooth muscle. We assessed denervation effects on viscoelastic properties of the aorta of Lewis Polycystic Kidney (LPK) disease rats, compared to controls (Lewis). Methods: Abdominal aortic pressure (intravascular, Scisence) and diameter (ultrasound, Artlab) was measured in anesthetised (urethane, 1.3 g/kg) Lewis (n=11) and LPK (n=5) rats before and following denervation by ganglionic blockade (intravenous hexamethonium, 20 mg/kg). Bolus intravenous doses of vasoactive agents (6 μg phenylephrine or sodium nitroprusside) were used to study the rats at mean pressures of 75, 100, 125 and 150 mmHg. Complex elastic modulus (Ec) was calculated from the Fourier decomposition of pressure and diameter. Viscoelasticity (VE=Im(Ec)) was compared between LPK and Lewis rats in the intact and denervated state across the first three harmonics. Pressure dependency of viscoelasticity was studied using a frequency (thus heart rate) normalised viscoelastic term (VEN=VE/frequency). Results: VE increased with frequency in all but Lewis rats at 150 mmHg. LPK rats had higher VE than Lewis (p<0.05), other than denervated rats at 150 mmHg and intact rats at 75 mmHg. Denervation reduced VE in both LPK and Lewis groups (p<0.05). VEN increased with pressure (p<0.001, Figure). Conclusions: Aortic viscoelasticty was generally greater in LPK rats and was reduced with denervation. This study shows possible relationships between aortic compliance in polycystic kidney disease and sympathetic dysregulation.