Mechanisms of rubidium permeation by rabbit cortical collecting duct during potassium restriction

Xiaoming Zhou, Charles S. Wingo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


To examine the pathways of K permeation in the cortical collecting duct (CCD) from K-restricted rabbits, we studied the effects of the following three maneuvers: 1) luminal amiloride addition; 2) luminal Ba addition; and 3) luminal Na removal. Luminal addition of amiloride (1 mM) significantly increased the 86Rb lumen-to-bath efflux coefficient (KRb), and this effect was fully blocked by the presence of 2 mM luminal Ba. Addition of 2 mM luminal Ba reduced KRb both in the absence of luminal Na and in the presence of luminal Na. In contrast to the effect of amiloride addition, removal of luminal Na significantly increased KRb, but neither 2 mM luminal Ba nor 4 mM luminal Ba totally abolished this effect. However, simultaneous addition of luminal Ba and Sch 28080 (10 μM) fully inhibited the increase in KRb upon luminal Na removal, indicating that luminal Na removal enhances Rb efflux in part via H-K-adenosmetriphosphatase (H-K-ATPase). To test whether Na acts as a partial agonist for cation efflux via the H-K-ATPase we examined the effect of Sch 28080 on the 22Na lumen-to-bath efflux coefficient (KNa). These studies were conducted in the presence of 0.1 mM luminal amiloride to block fully apical conductive Na efflux, and the effect of Sch 28080 on XNa was examined at two different ambient K concentrations. In the presence of 0.5 mM K, Sch 28080 (10 μM) significantly inhibited KNa from 47.6 ± 4.8 to 35.0 ± 6.8 nm/s (P < 0.005). In contrast, the effect of Sch 28080 on KNa was abolished when similar experiments were performed in the presence of 20 mM K. Moreover, 20 mM K did not abolish the effect of Sch 28080 on KRb. From these data we conclude that 1) an apical Ba-sensitive K conductance mediates the stimulation of KRb by amiloride; 2) both a Ba-sensitive K conductance and the H-K-ATPase mediate the enhancement of KRb after luminal Na removal; and 3) Na can compete with K for transport via the H-K-ATPase.

Original languageEnglish
Pages (from-to)F1134-F1141
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Issue number6 32-6
StatePublished - Dec 1992
Externally publishedYes


  • Amiloride
  • Barium
  • Potassium channels
  • Proton-potassium-adenosinetriphosphatase
  • Sodium


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