Abstract
Ureteral obstruction causes impaired salt wastage and K+ secretion in the distal nephron segments, including the cortical collecting duct (CCD). Recently, we demonstrated that conductances of Na+ and K+ in the apical membrane, as well as the electrogenic Na(+)-K+ pump activity and the relative K+ conductance in the basolateral membrane of the collecting duct cell, were inhibited in the obstructed kidney after unilateral ureteral obstruction (UUO). To examine whether the increased intrarenal pressure might be causally related to these abnormalities in the CCD, the effects of unilateral renal decapsulation, a maneuver that partially blocks the increase in renal pressure, were evaluated with microelectrode techniques in isolated CCDs from UUO and sham-operated (control) rabbits 24 h after operation. Renal decapsulation had no effects on barrier voltages and conductances in the CCD from control animals. The lumen-negative transepithelial (VT) and basolateral membrane (VB) voltages as well as the transepithelial (GT) and the apical membrane (GA) conductances were decreased in the CCD from UUO animals compared with control animals. Pretreatment of renal decapsulation partially corrected the decreases in VT, VB, GT, and GA seen in the CCD from UUO animals. The changes in apical membrane voltage and GT upon addition of luminal amiloride and Ba2+, and the changes in VB upon addition of bath ouabain, were also decreased in the CCD from UUO animals compared with control animals. Pretreatment of renal decapsulation also partially corrected the above abnormalities seen in UUO animals, whereas it had no effect in control animals. The transference numbers for Cl- (tCl) and K+ (tK) in the basolateral membrane were, respectively, increased and decreased in the CCD from UUO animals compared with control animals. Pretreatment of renal decapsulation also partially corrected the changes in tCl and tK seen in UUO animals, whereas it had no effect in control animals. We conclude that, in UUO animals, renal decapsulation partially corrects the inhibition of apical Na+ and K+ conductances as well as basolateral Na(+)-K+ pump activity and relative K+ conductance seen after UUO, whereas in control animals it has no effect. The increased renal pressure may partly contribute to the defects in Na+ and K+ transport in the CCD from obstructed kidneys. Renal decapsulation has protective effects on impaired Na+ and K+ transports in the CCD after ureteral obstruction.