The apical na+ conductance in the maturing rabbit principal
cell.
Satlin, Lisa M., and Lawrence G. Palmer.
Department of Pediatrics, Albert Einstein College of Medicine, 1410
Pelham Pkwy South, Bronx, New York 10461 and Department of Physiology
and Biophysics, Cornell University Medical College, New York, New
York 10021
APStracts 2:0144F, 1995.
Net Na+ absorption in microperfused rabbit cortical collecting ducts
(CCDs) is low during the 1st wk of postnatal life, increasing
substantially thereafter (Am. J. Physiol. 266:F57, 1994). To
establish whether the low rate of Na+ absorption observed immediately
after birth is due to a low apical Na+ permeability of the neonatal
principal cell, we used the patch-clamp technique in split-open CCDs
isolated from maturing rabbits to estimate conductance, number (N),
and open probability (Po) of apical Na+ channels in principal cells.
With LiCl in the pipette and a NaCl or K-gluconate solution, warmed
to 37oC, in the bath, inward currents with a conductance of 11 pS
(n=23) were observed in 17% of cell-attached patches at 1 wk, 41% of
patches at 2 wks and 43% of patches at 5 wks. The mean number of
channels per patch in the 1st wk (0.22+/-0.09; n=36) was
significantly less than that observed in the 2nd (1.38+/-0.39; n=34)
and 5th (1.24+/-0.37; n=21) wks of life. Po, studied at positive
pipette voltages, was significantly lower in the 1st wk (0.085+/
-0.035; n=5) than at 2 wks (0.345+/-0.063; n=9) and 5 wks of age
(0.291+/-0.058; n=4). To confirm that the 11 pS channel represented
the amiloride-sensitive apical Na+ channel, cell-attached patches in
CCDs isolated from 2-wk-old rabbits were studied with 0.5 [mu]M
amiloride added to the LiCl pipette solution. Amiloride led to
>90% reductions in mean open and closed times of the 11 pS
conductance, consistent with blockade of the channel. These data
indicate that N and Po of apical amiloride-sensitive Na+ channels in
principal cells increases significantly after birth.
Received 24 May 1995; accepted in final form 15 August 1995.
APS Manuscript Number F163-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 August 1995.