Mineralocorticoid receptor-mediated signaling regulates the ion gated sodium channel in vascular endothelial cells and requires an intact cytoskeleton

The PCR analysis followed by sequence alignment showed that both the minera locorticoid receptor (MCR) and the epithelial sodium channel (ENaC) genes w ere expressed in the human vascular endothelial cell line (ECV). The growth and multiplication of the ECV in culture were influenced by both aldostero ne and the MCR-specific antagonist ZK 91587. Following double labelled immu nofluorescence recorded by confocal microscopy, both the MCR and the ENaC w ere found to colocalize with the tubulin filaments in ECV cells in situ; no association was observed with cellular actin, ZK 91587 not only eliminated the basal expression, but it also impaired the transactivation of the ENaC gene by aldosterone. The disruption of actin and tubulin by cytochalasin D and colchicine, respectively, resulted in the total elimination of ENaC in duction by aldosterone. These studies suggest that (i) the transcriptional regulation of the ENaC gene by the MCR-mediated signalling is not restricte d to epithelial cells and requires cytoskeleton integrity in ECV cells in s itu, (ii) tubulin may form a new and novel mediator in cell regulation, and (iii) the vascular tone may actually be regulated via transactivation of t he ion gated sodium channel in the endothelial cell of the blood vessels un der direct, receptor-mediated action of aldosterone. (C) 2001 Academic Pres s.