Abstract 12265: Normalization of Renal AT1 Receptor Expression is Observed With Enalapril But Not Diltiazem in a Rat Model of Chronic Kidney Disease

Abstract

Introduction: Use of ACE inhibitors (ACEi) improves outcomes in patients with proteinuric chronic kidney disease (CKD) and is considered first line of treatment in recent guidelines. In addition to renin angiotensin (Ang) system blockers, other antihypertensive agents such as calcium channel blockers (CCBs) achieve similar therapeutic effectiveness in renoprotection. Our objective was to determine the impact of antihypertensive therapy on renal Ang type 1 receptor (AT 1 R) in 5/6 subtotal nephrectomy (Nx) rat model of CKD using PET imaging. Methods: Ten weeks after Nx, Sprague-Dawley rats (n=6-8/group) were administered 10mg/kg/d enalapril (NxE), 30 mg/kg/d diltiazem (NxD) or left untreated (Nx) for an additional ∼10 weeks. Systolic blood pressure (SBP), plasma creatinine, urine albumin, plasma and tissue Ang II were measured at the end. AT 1 R was assessed using in vivo [ 18 F]FPyKYNE-losartan PET and in vitro autoradiography. Heart function was evaluated with echocardiography. Results: Compared to shams, Nx rats exhibited higher SBP that was reduced by both enalapril and diltiazem (142.7±2, 188.8±17.3, 152±8.7 and 145.8±5.8 mm Hg in sham, Nx, NxE and NxD, respectively, p <0.05). At ∼20 weeks, plasma creatinine and albuminuria were significantly increased in Nx rats, while no changes occurred in NxE rats compared to shams. By contrast, NxD rats demonstrated further increases in these parameters, compared to Nx alone ( p <0.05). Plasma and kidney Ang II were raised in Nx rats, lowered by enalapril and increased significantly in NxD rats ( p <0.05). PET kidney AT 1 R level decreased in Nx rats compared to shams and only enalapril treatment normalized AT 1 R expression (2.8±0.5, 2±0.3, 2.9±0.6, 1.9±0.5 ml/cm 3 in sham, Nx, NxE and NxD respectively, p <0.05) and was confirmed by in vitro results. Enhanced echo LV mass in Nx rats was not reversed by enalapril but was further increased with diltiazem ( p <0.001). Conclusions: In rats with CKD, delayed treatment with the ACEi enalapril normalized AT 1 R expression and reduced progression of the disease, whereas the CCB diltiazem exacerbated renal and cardiac dysfunctions. [ 18 F]FPyKYNE-Losartan PET allows longitudinal determination of AT 1 R abnormalities with progression of cardiorenal failure and monitoring of therapy.