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