The collecting tubule of Amphiuma. I. Electrophysiological characterization.
Single collecting tubules of Amphiuma kidneys were perfused in vitro to characterize their electrophysiological properties. The lumen-negative potential (-24 mV) was abolished by amiloride in the lumen and by ouabain in the bath. Ion substitution experiments in the lumen demonstrated the presence of a large sodium conductance in the apical cell membrane, but no evidence was obtained for a significant potassium or chloride conductance. Ion substitutions in the bath solution and the depolarizing effect of barium on the basolateral membrane potential demonstrated the presence of a large potassium conductance in the basolateral cell membrane. Measurements of dilution potentials in amiloride-treated tubules revealed a modest cation selectivity of the paracellular pathway. These results support a cell model in which sodium reabsorption occurs by electrodiffusion across the apical cell membrane and active transport across the basolateral cell membrane. The absence of a detectable potassium conductance in the apical cell membrane suggests that secretion of this ion cannot take place by diffusion from cell to lumen.
Hunter
M
M
Department of Physiology, Yale University School of Medicine, New Haven, Connecticut 06510.
Horisberger
J D
JD
Stanton
B
B
Giebisch
G
G
D000465:Algorithms; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D004553:Electric Conductivity; D004594:Electrophysiology; D005260:Female; D007684:Kidney Tubules / Q000502:physiology*; D007685:Kidney Tubules, Collecting / Q000502:physiology*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D012016:Reference Values; D014562:Caudata / Q000502:physiology*
D001464:Barium; D010042:Ouabain; D000584:Amiloride