Apical K+ conductance in maturing rabbit principal cell.
Net K+ secretion is not detected in cortical collecting ducts (CCDs) isolated from newborn rabbits and perfused in vitro. To establish whether a low apical K+ permeability of the neonatal principal cell limits K+ secretion early in life, we used the patch-clamp technique in split-open CCDs isolated from maturing rabbits to study the properties and density of conducting K+ channels in principal cells. With KCl in the pipette and a NaCl solution warmed to 37 degrees C in the bath, inward currents with a conductance of approximately 42 pS were observed in 0% (0 out of 13 or 0/13), 10% (2/21), 18% (5/28), 29% (4/14), and 56% (10/18) of cell-attached patches obtained in 1-, 2-, 3-, 4-, and 5-wk-old animals, respectively. The conductance and reversal potential of this channel led us to suspect that it represented the low-conductance K+ channel previously described in the rat CCD by L. G. Palmer, L. Antonian, and G. Frindt (J. Gen. Physiol. 104: 693-710, 1994). The mean number of open channels per patch (NPo) increased progressively (P < 0.05) after birth, from 0 at 1 wk, to 0.06 +/- 0.04 at 2 wk, to 0.40 +/- 0.18 at 3 wk, to 0.74 +/- 0.41 at 4 wk, and to 1.06 +/- 0.28 at 5 wk. The increase in NPo appeared to be due primarily to a developmental increase in N, which is the number of channels; open probability, Po, remained constant at approximately 0.5 for all channels identified after the 2nd wk of life. The increase in number of conducting K+ channels during postnatal life is likely to contribute to the maturational increase in net K+ secretion in the CCDs.
Satlin
L M
LM
Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Palmer
L G
LG
D000375:Aging / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D004553:Electric Conductivity; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000254:growth & development / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D051381:Rats
D015221:Potassium Channels; D011189:Potassium Chloride