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Nuclear Membranes ETB Receptors Mediate ET-1–induced Increase of Nuclear Calcium in Human Left Ventricular Endocardial Endothelial Cells

Abstract: In fetal human left ventricular endocardial endothelial cells (EECLs), both plasma membrane (PM) ETAR and ETBR were reported to mediate ET-1–induced increase of intracellular calcium [Ca]i; however, this effect was mediated by ETAR in right EECs (EECRs). In this study, we verified whether, as for the PM, nuclear membranes (NMs) ET-1 receptors activation in EECLs and EECRs induce an increase of nuclear calcium ([Ca]n) and if this effect is mediated through the same receptor type as in PM. Using a plasmalemma-perforated technique and 3D confocal microscopy, our results showed that, as in PM intact cells, superfusion of nuclei of both cell types with cytosolic ET-1 induced a concentration-dependent sustained increase of [Ca]n. In EECRs, the ETAR antagonist prevented the effect of ET-1 on [Ca]n without affecting EECLs. However, in both cell types, the effect of cytosolic ET-1 on [Ca]n was prevented by the ETBR antagonist. In conclusion, both NMs' ETAR and ETBR mediated the effect of cytosolic ET-1 on [Ca]n in EECRs. In contrast, only NMs' ETBR activation mediated the effect of cytosolic ET-1 in EECLs. Hence, the type of NMs' receptors mediating the effect of ET-1 on [Ca]n are different from those of PM mediating the increase in [Ca]i.