Rapid effects of 17β-estradiol on TRPV5 epithelial Ca2+ channels in rat renal cells

The renal distal tubules and collecting ducts play a key role in the control of electrolyte and fluid homeostasis. The discovery of highly calcium selective channels, Transient Receptor Potential Vanilloid 5 (TRPV5) of the TRP superfamily, has clarified the nature of the calcium entry channels. It has been proposed that this channel mediates the critical Ca2+ entry step in transcellular Ca2+ re-absorption in the kidney. The regulation of transmembrane Ca2+ flux through TRPV5 is of particular importance for whole body calcium homeostasis.In this study, we provide evidence that the TRPV5 channel is present in rat cortical collecting duct (RCCD2) cells at mRNA and protein levels. We demonstrate that 17β-estradiol (E2) is involved in the regulation of Ca2+ influx in these cells via the epithelial Ca2+ channels TRPV5. By combining whole-cell patch–clamp and Ca2+-imaging techniques, we have characterized the electrophysiological properties of the TRPV5 channel and showed that treatment with 20–50 nM E2 rapidly (<5 min) induced a transient increase in inward whole-cell currents and intracellular Ca2+ via TRPV5 channels. This rise was significantly prevented when cells were pre-treated with ruthenium red and completely abolished in cells treated with siRNA specifically targeting TRPV5.These data demonstrate for the first time, a novel rapid modulation of endogenously expressed TRPV5 channels by E2 in kidney cells. Furthermore, the results suggest calcitropic effects of E2. The results are discussed in relation to present concepts of non-genomic actions of E2 in Ca2+ homeostasis.