Difference in the response to angiotensin II between left and right ventricular endocardial endothelial cells

Previous studies focused on the right ventricular endocardial endothelial cells (EECRs) and showed that angiotensin II (Ang II) induced increase in cytosolic and nuclear calcium via AT 1 receptor activation. In the present study, we verified whether the response of left EECs (EECLs) to Ang II is different than that of EECRs. Our results showed that the EC 50 of the Ang II-induced increase of cytosolic and nuclear calcium in EECLs was 10× higher (around 2 × 10 −13 mol/L) than in EECRs (around 8 × 10 −12 mol/L). The densities of both AT 1 and AT 2 receptors were also higher in EECLs than those previously reported in EECRs. The effect of Ang II was mediated in both cell types via the activation of AT 1 receptors. Treatment with Ang II induced a significant increase of cytosolic and nuclear AT 1 receptors in EECRs, whereas the opposite was found in EECLs. In both cell types, there was a transient increase of cytosolic and nuclear AT 2 receptors following the Ang II treatment. In conclusion, our results showed that both AT 1 and AT 2 receptors densities are higher in both EECLs compared to what was reported in EECRs. The higher density of AT 1 receptors in EECLs compared to REECs may explain, in part, the higher sensitivity of EECLs to Ang II.