The α1G-subunit of a voltage-dependent Ca2+ channel is localized in rat distal nephron and collecting duct

Abstract

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 α1G-subunit encoding a voltage-dependent calcium channel with T-type characteristics. Using a RNase protection assay, α1G-mRNA levels in kidney regions were determined as inner medulla ≫ outer medulla ≅ cortex. RT-PCR analysis of microdissected rat nephron segments revealed α1G expression in the distal convoluted tubule (DCT), in the connecting tubule and cortical collecting duct (CT+CCD), and inner medullary collecting duct (IMCD). α1GmRNA 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-α1G antibody demonstrated a distinct labeling at the apical plasma membrane domains of DCT cells, CT principal cells, and IMCD principal cells.