Gilman, Gregory

Decreased renal function is associated with increased CV morbidity and mortality. However, the impact of mild renal dysfunction upon the heart remains to be fully elucidated. It is thought that a mild reduction in renal mass is not deleterious to the heart, yet exploration of the impact of unilateral nephrectomy (Nx) on myocardial gene responses is undefined. We hypothesized that even when ventricular function and structure are grossly preserved after Nx, such a reduction in renal mass and function would result in significant alterations in the cardiac genome. Wistar rats, Sham(S)(n=10), Nx(n=9). 4 weeks after Nx we assessed proteinuria, UNaV, UcGMP and BNP. Cardiac function was assessed by echo. GFR was determined by inulin clearance and renal blood flow (RBF) by PAH. Blood was obtained for BNP, aldosterone and cGMP. Kidneys and hearts were harvested. Gene microarrays were conducted of left ventricle (LV) myocardium (Affymetrix GeneChip® Rat Genome 230 2.0). GFR strongly tended to decrease and RBF was decreased in Nx (S:8±1, Nx:5±1 ml/min, p<0.005). Glomerular volume was increased in Nx (S:1±0.04, Nx:1.6±0.1 u 3 ×10 6 , p<0.001) while UNaV and volume were not different. There was no proteinuria in Nx. EF, LV end systolic and diastolic diameters were normal. Blood pressure (BP) was unchanged. There was no activation of the systemic RAAS or BNP. Importantly, 278 cardiac genes changed their expression after Nx (1.5 fold, P<0.05). 11% were increased and 89% decreased. Pathways involved included cell adhesion, growth and proliferation. We conclude that Nx, independently of alterations in circulating RAAS or BNP, BP or myocardial structure and function, results in widespread changes in myocardial gene expression. Further long‐term studies are needed to define the impact of these early gene responses to myocardial structure and function.