The effects of changes of water balance on the renal pelvic epithelium of the rat.

The effects of changes of water balance on the renal pelvic epithelium of the rat. The fine structure of the various epithelia which line the renal pelvis was investigated in five hydropenic rats and five rats undergoing a water diuresis. In the former, the thin epithelium which covers the outer medulla showed dilated intercellular spaces and an increased number of cytoplasmic vacuoles whereas the intercellular spaces were tightly closed and there were few vacuoles in the diuretic rats. It was considered that these changes indicate an exchange of water and solute between pelvic urine and the outer since medulla they are similar to those occurring in epithelia elsewhere which are engaged in transport of salt or water. Similar but less marked changes were found in the papillary epithelium. Changes in the transitional epithelium were similar to those which have previously been described elsewhere in the urinary tract.