A Ca2+ channel in renal epithelial cells introduced by parathyroid hormone

To investigate the mechanism of Ca2+ influx after hormonal stimuli, patch clamping with [Ca2+]i fluorescence measurement was performed in single renal proximal epithelial cells. A Ca2+ current appeared along with a rise in [Ca2+]i during parathyroid hormone addition to the bath, but not when the hormone was inside the cell-attached pipette. The Ca2+ channel, possessing linear I-V, was nonselective for cations, most active in hyperpolarized--membranes and showed oscillatory fluctuations in opening, which disappeared after excision. GTP gamma S opened the channel that had disappeared, which was suppressed by GDP beta S. These data show a PTH-responsive Ca2+ channel for which GTP/GDP may act as second messenger to open the latent Ca2+ channel.