Localization of thiazide-sensitive NaCl cotransport and associated gene products in the mouse distal convoluted tubule

The mammalian distal nephron develops a complex assembly of specialized cell types to accomplish the fine adjustment of urinary electrolyte composition. The epithelia of the distal convoluted tubule (DCT), the connecting tubule (CNT) and the cortical collecting duct (CCD) show an axial structural heterogeneity that has been functionally elucidated by the localization of proteins involved in the transepithelial ion transport. We compared the distribution of the thiazide-sensitive Na+,Clcotransporter (TSC), the basolateral Na+/Ca++ exchanger (Na/Ca), the cytosolic calcium-binding proteins, calbindin D28K and parvalbumin, and the key enzyme for selective aldosterone actions, 11ß-hydroxysteroid-dehydrogenase 2 (11HSD2), in the distal convolutions of the mouse. The mouse differs from the rat in that we found no clear subsegmentation of the DCT into a proximal (DCT1) and a distal (DCT2) portion. The TSC was expressed along the entire DCT. The Na/Ca and calbindin D28K were similarly expressed along most of the DCT with minor exceptions in the initial portion of the DCT. Both were also present in the CNT. Parvalbumin was found in the entire DCT with occasional absence from short end portions of the DCT, and was not present in CNT. 11HSD2 was predominantly located in the CNT and CCD. Short end portions of DCT only occasionally showed the 11HSD2 signal. We also observed overlap of 11HSD2 immunoreactivity and mRNA staining. Our observations will have implications in understanding the physiological effects of gene disruption and targeting experiments in the mouse.