Electrical properties of the rabbit cortical collecting duct from obstructed and contralateral kidneys after unilateral ureteral obstruction.

Abstract

IntroductionElectrophysiological techniques were used to determine the electrical properties of the collecting duct (CD) cell in the isolated cortical collecting duct from obstructed (UUOOK) and contralateral (UUOcK) kidneys in rabbits 24 h after unilateral ureteral obstruction (UUO); results were compared with those from sham-operated kidneys. The lumen-negative transepitheHal voltage and the basolateral membrane voltage (V B) were decreased in the UUOOK, and increased in the UUOCK. The transepithelial conductance (GT) was decreased in parallel with an increase in the fractional apical membrane resistance (fRA) and a decrease in apical membrane conductance in the UUOOK. By contrast, the GT was increased in parallel with increases in apical and basolateral membrane conductances in the UUOCK. The amiloride-sensitive changes in apical membrane voltage (V A), GT and f RA were lower in the UUOOK, but greater in the UUOCK. The changes in V A and GT upon raising the perfusate K+ concentration and upon addition of luminal Ba2" were decreased in the UUOOK, and increased in the UUOCK. Addition of ouabain to the bath resulted in a smaller depolarization ofV B in the UUOOK, but in a greater depolarization in the UUOCK. Upon lowering bath Cl-, the change in basolateral membrane electromotive force (AEMF) was increased in the UUOOK, and decreased in the UUOCK. Reversely, upon raising bath K+, the AEMF was decreased in the UUOOK, and increased in the UUOCK. We conclude: (a) the conductances of Na+ and K+ in the apical membrane, and active Na+-K+ pump activity and relative K+ conductance in the basolateral membrane are decreased in the UUOOK, and increased in the UUOCK; (b) the relative basolateral membrane CI-conductance was increased in the UUOOK, and decreased in the UUOCK. Unilateral ureteral obstruction (UUO)' causes a number of alterations in renal function ofboth obstructed and untouched contralateral kidneys ( 1, 2). Abnormalities in Na+ and water conservation and in H+ and K+ excretion (3-9) are known to occur in the distal nephron segments, including the cortical collecting duct (CCD), from the obstructed kidney after UUO. However, the mechanisms underlying these disorders have not been fully evaluated. Only a few studies have assessed some of them at a segmental level. The in vitro microperfusion studies of the rabbit CCD have demonstrated that ureteral obstruction led to decreases in the lumen-negative transepithelial voltage (6, 8) as well as in Na+ reabsorption (6). These changes also included decreases in Na+-K+-ATPase activity (9) and in Na+-K+ pump in situ turnover (4) in the CCD from the obstructed rat kidney after UUO. These observations have suggested that the collecting duct (CD) cell would be functionally impaired after ureteral obstruction, because the CD cell is mainly responsible for Na+ and K+ transports in the CCD (10-15). However, the cellular mechanisms of the defects in Na+ and K+ transports in the CCD from obstructed kidneys remain unknown.In addition, there is little information regardi...

Electrical properties of the rabbit cortical collecting duct from obstructed kidneys after unilateral ureteral obstruction. Effects of renal decapsulation.

“…Slices of the coronal section 1-2-mm thick from left kidneys were made and transferred to a dish containing a cold intracellular fluid-like solution of the following composition (mM): 14 KCl, 44 K2HPO4, 14 KH2PO4, 9 NaHCO3, and 160 sucrose. As described previously (20)(21)(22)(23)(24)(25)(26)(27), this dissection medium was selected because it has been reported that intracellular fluid-like solutions are much better at preserving kidney tissue, metabolically as well as functionally. Segments of CCDs were dissected from the cortex and transferred to a bath mounted on an inverted microscope (Diaphot; Nikon, Tokyo, Japan).…”

“…Segments of CCDs were dissected from the cortex and transferred to a bath mounted on an inverted microscope (Diaphot; Nikon, Tokyo, Japan). Each tubule was perfused in vitro according to the techniques developed by Burg et al (31) and as modified in this laboratory for the use of intracellular microelectrodes (20)(21)(22)(23)(24)(25)(26)(27). Since the details of the technique have been published previously (20)(21)(22)(23)(24)(25)(26)(27), they will be presented here only briefly.…”

“…The transepithelial and cellular electrical properties of the tubule were measured using techniques described previously in this laboratory (20)(21)(22)(23)(24)(25)(26)(27). In brief, the transepithelial voltage (VT) was measured through the perfusion pipette, which was connected to one channel of a dual-channel electrometer (Duo 773; World Precision Instruments, Inc., Sarasota, FL) with a 3 M KCI/3% agar bridge and a calomel half-cell electrode.…”

“…Both voltages were referenced to the bath and were recorded on a four-pen chart recorder (R64; Rikadenki, Tokyo, Japan). The electrical potential difference across the apical membrane (VA) was given by VA = VT -VB Cable analysis was used to calculate the transepithelial conductance (GT) and the fractional apical membrane resistance (fRA), as described in detail previously (20)(21)(22)(23)(24)(25)(26)(27). Constant-current pulses, 50 nA (300 ms in duration, 10-s interval), were injected into the tubule lumen via the perfusion pipette.…”

“…The in vitro microperfusion studies of the rabbit CCD have demonstrated that unilateral ureteral obstruction (UUO) led to decreases in the lumen-negative transepithelial voltage (10,11) as well as in Na'-K+-ATPase activity (12) and in Na'-K' pump in situ turnover (13) in the CCD from obstructed rat kidneys after UUO. These observations have suggested that the collecting duct (CD) cell would be functionally impaired after ureteral obstruction, since the CD cell is mainly responsible for Na' and K+ transports in the CCD (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). Very recently, Muto et al (25) have demonstrated that in the rabbit CCD from obstructed kidneys 24 h after UUO conductances of Na' and K+ in the apical membrane as well as electrogenic Na'-K+-ATPase pump activity and relative K+ conductance in the basolateral membrane of the CD cell were inhibited, whereas the relative Cl-conductance in the basolateral membrane was stimulated.…”