Differential Right and Left Ventricular Diastolic Tolerance to Acute Afterload and NCX Gene Expression in Wistar Rats

J. CORREIA PINTO, T. HENRIQUES-COELHO,
R. RONCON-ALBUQUERQUE Jr, A. F. LEITE-MOREIRA

Department of Physiology, Faculty of Medicine, University of Porto, Porto, Portugal.

Received date August 12, 2005
Accepted date December 11, 2005
On-line available December 12, 2005


Summary
This study evaluated right ventricular (RV) and left ventricular (LV) diastolic tolerance to afterload and SERCA2a, phospholamban and sodium-calcium exchanger (NCX) gene expression in Wistar rats. Time constant and end diastolic pressure-dimension relation (EDPDR) were analyzed in response to progressive RV or LV afterload elevations, induced by beat-to-beat pulmonary trunk or aortic root constrictions, respectively. Afterload elevations decreased LV-, but increased RV-. Whereas LV- analyzed the major course of pressure fall, RV- only assessed the last fourth. Furthermore, RV afterload elevations progressively upward shifted RV EDPDR, whilst LV afterload elevations did not change LV-EDPDR. SERCA2a and phospholamban mRNA were similar in both ventricles. NCX-mRNA was almost 50 % lower in RV than in LV. Left ventricular afterload elevations, therefore, accelerated the pressure fall and did not induce diastolic dysfunction, indicating high LV diastolic tolerance to afterload. On the contrary, RV afterload elevations decelerated the late RV pressure fall and induced diastolic dysfunction, indicating small RV diastolic tolerance to afterload. These results support previous findings relating NCX with late Ca2+ reuptake, late relaxation and diastolic dysfunction.


Key words
Gene expression • Hemodynamics • Na/Ca-exchanger • Ventricular function • Diastole