The possible involvement of calcium in renal proximal tubular reabsorptive defect in the rat after release of ureteral obstruction

The temporal relationship between changes in cytosolic free calcium and proximal tubular function was examined in rats following 24 h of unilateral and bilateral ureteral obstruction. Immediately after release of unilateral ureteral obstruction, proximal tubular functions were found to be normal. Cytosolic free calcium in isolated proximal tubules of the ureteral obstructed and contralateral kidneys were 160 +/- 8 and 172 +/- 15 nM, respectively. On the 7th day after release, cytosolic free calcium was not different from the sham control value (135 +/- 6 vs. 149 +/- 7 nM). In contrast, immediately after release of bilateral ureteral obstruction, cytosolic free calcium was increased significantly to 219 +/- 6 from 139 +/- 9 nM in sham-operated controls. Subsequent declines in cytosolic free calcium to 196 +/- 15 and 148 +/- 7 nM were observed at 3 and 7 days after release of bilateral ureteral obstruction, respectively. Over this period, renal tubular functions gradually returned to normal. Changes in cytosolic free calcium correlate well with the reported improvement in renal tubular function after release of bilateral ureteral obstruction. Therefore, one possible mechanism for the impairment of tubular function observed in bilateral ureteral obstruction may be an increase in cytosolic free calcium.