Uptake of Pi in basolateral vesicles after release of unilateral ureteral obstruction.

We previously demonstrated Na+-dependent 32Pi uptake in basolateral membrane vesicles from kidneys of normal dogs. We postulated that this reflects Na+-dependent Pi transport across the basolateral membrane into the proximal tubular cell in vivo that subserves cellular needs for Pi. To ascertain whether Pi transport across the basolateral membrane was enhanced in a condition in which delivery of Pi across the luminal membrane would be markedly decreased, we measured Na+-dependent 32Pi uptake in basolateral vesicles isolated from postobstructed and control kidneys of dogs following release of unilateral ureteral obstruction. Clearance of creatinine and filtered load of Pi were significantly decreased in postobstructed compared with control kidneys. Na+-dependent 32Pi uptake was increased in basolateral vesicles from postobstructed compared with control kidneys, as reflected by increased initial rate of uptake and an increased overshoot of 32Pi transport. Our findings are consistent with an adaptation resulting in increased transport of Pi across the basolateral membrane of the proximal tubular cell in unilateral ureteral obstruction. This process may provide required Pi to the cell under conditions in which decreased Pi is available for transport across the brush border membrane.