Thiazide treatment of rats provokes apoptosis in distal tubule cells

We studied the effects of inhibition of apical NaCl entry on the structural correlates for electrolyte transport in the distal convoluted tubule (DCT) of rats. Thiazide diuretics were used to block NaCl entry specifically in the DCT. Metolazone or hydrochIorothiazide (HCTZ) were applied fur three days subcutaneously via osmotic minipumps. The renal epithelial structure of control and treated rats was studied by light and electron microscopy. Distribution of the thiazide-sensitive NaCl cotransporter (rTSC1), calbindin D-28K and Ca2+-Mg2+-ATPase was examined by immunohistochemistry, and the content of rTSC1 transcripts by Northern blot and iii situ hybridization. In treated rats the DCT epithelium had lost the structural characteristics of electrolyte transporting epithelia and the cells were in different stages of apoptosis. In damaged cells calbindin D-28K and Ca2+-Mg2+-ATPase were strongly decreased the rTSCl was shifted from the luminal membrane to the basal cell half and was found additionally in small membrane vesicles in intercellular and peritubular spaces. Transcripts of rTSC1 were drastically reduced in homogenates of kidney cortex and almost absent in damaged DCT cells, Ali other tubular segments were unaffected by the treatment. Focal inflammatory infiltrates were found to be specifically surrounding DCT profiles. Thus, inhibition by thiazides of apical NaCl entry into DCT cells is associated with apoptosis of DCT cells and focal peritubular inflammation.