The α(1G)-subunit of a voltage-dependent CA²⁺ channel is localized in rat distal nephron and collecting duct

The molecular type and localization of calcium channels along the nephron are not well understood. In the present study, we assessed the distribution of the recently identified α(1G)-subunit encoding a voltage-dependent calcium channel with T-type characteristics. Using a RNase protection assay, α(1G)mRNA levels in kidney regions were determined as inner medulla > > outer medulla ≃ cortex. RT-PCR analysis of microdissected rat nephron segments revealed α(1G) expression in the distal convoluted tubule (DCT), in the connecting tubule and cortical collecting duct (CT+CCD), and inner medullary collecting duct (IMCD). α(1G) mRNA was expressed in the IMCD cell line mIMCD-3. Single- and double-labeling immunohistochemistry and confocal laser microscopy on semithin paraffin sections of rat kidneys by using an anti-α(1G) antibody demonstrated a distinct labeling at the apical plasma membrane domains of DCT cells, CT principal cells, and IMCD principal cells.