Cell swelling activates basolateral membrane Cl and K conductances in rabbit proximal tubule

P. A. Welling, R. G. O'Neil

Research output: Contribution to journalArticle

Abstract

The ionic basis of volume regulation was assessed in the nonperfused rabbit proximal tubule (S2 segment) by use of simultaneous measurements of tubule volume via video-optical imaging techniques and basolateral membrane voltage (V(bl)) and relative ionic conductance via conventional microelectrodes. Both cell volume (9.9 ± 0.70 nl/cm tubule length) and V(bl) (-42.8 ± 3.6 mV) remained stable in the control isotonic Ringer solution (290 mosmol/kg). When the osmolality of the bathing medium was reduced to 150 mosmol/kg, tubules swelled 72% above base line within 1 min and subsequently regulated over the course of the mext 4-6 min to a steady state 20 ± 3% above the initial base-line volume. Cell swelling was accompanied by a transient hyperpolarization of V(bl) of -14.3 ± 2.0 mV (HCO3-containing Ringer) and -10.0 ± 0.7 mV (HCO3-free Ringer). Although the hyperpolarization was not inhibited by barium in the presence of bicarbonate buffer, addition of 2 mM Ba to a bicarbonate-free Ringer depolarized V(bl) by +22 mV and abolished both the relative potassium conductance and the hyperpolarization accompanying cell swelling (ΔV(bl) = -4.6 ± 0.6 mV). Furthermore, the relative conductance of K at the basolateral membrane increased from 0.16 in the isotonic control medium to 0.34 at the peak of cell swelling. Because the hyperpolarization of V(bl) ensued after cells had swollen ~ 10% above base line, a modest threshold volume and time delay may be involved in triggering the volume-dependent activation of the K conductance. In parallel studies, the change in V(bl) on a rapid step-change in bath Cl (49 to 4.9 mM) averaged 5.3 ± 1.0 mV in the isotonic solution and increased to +11.3 ± 2.1 (P ≤ 0.05) at the peak of cell swelling. This represented an increase in the relative Cl conductance of 0.08 to 0.20, which could only be attributed to an absolute increase in the basolateral membrane Cl conductance and not to a reduction in the other major basolateral membrane conductances. It is concluded that cell swelling results in an increase in both Cl and K conductance, which may underlie subsequent cell volume regulation.

Original languageEnglish (US)
Pages (from-to)F951-F962
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume258
Issue number4 27-4
DOIs
StatePublished - 1990

Keywords

  • 4-acetamido-4'-isothiocyanostilbene-2,2'- disulfonic acid
  • barium
  • bicarbonate
  • epithelium
  • osmolarity
  • proximal straight tubule
  • renal tubule
  • volume regulation
  • water transport

ASJC Scopus subject areas

  • Physiology

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