The mechanism of Na+ transport by rabbit urinary bladder
- 1 December 1976
- journal article
- research article
- Published by Springer Nature in The Journal of Membrane Biology
- Vol. 28 (1) , 41-70
- https://doi.org/10.1007/bf01869690
Abstract
The mechanism of Na+ transport in rabbit urinary bladder has been studied by microelectrode techniques. Of the three layers of epithelium, the apical layer contains virtually all the transepithelial resistance. There is radial cell-to-cell coupling within this layer, but there is no detectable transverse coupling between layers. Cell coupling is apparently interrupted by intracellular injection of depolarizing current. The cell interiors are electrically negative to the bathing solutions, but the apical membrane of the apical layer depolarizes with increasingI sc. Voltage scanning detects no current sinks at the cell junctions or elsewhere. The voltage-divider ratio, α, (ratio of resistance of apical cell membrane,R a, to basolateral cell membrane,R b) decreases from 30 to 0.5 with increasingI sc, because of the transportrelated conductance pathway in the apical membrane. Changes in effective transepithelial capacitance withI sc are predicted and possibly observed. The transepithelial resistance,R t, has been resolved intoR a, Rb, and the junctional resistance,R j, by four different methods: cable analysis, resistance of uncoupled cells, measurements of pairs of (R t, α) values in the same bladder at different transport rates, and the relation betweenR t andI sc and between α andI sc.R j proves to be effectively infinite (nominally 300 kΩ μF) and independent ofI sc, andR a decreases from 154 to 4 kΩ μF with increasingI sc. In the resulting model of Na+ transport in “tight” epithelia, the apical membrane contains an amiloride-inhibited and Ca++-inhibited conductance pathway for Na+ entry; the basolateral membrane contains a Na+−K+-activated ATPase that extrudes Na+; intracellular (Na+) may exert negative feedback on apical membrane conductance; and aldosterone acts to stimulate Na+ entry at the apical membrane via the amiloride-sensitive pathway.This publication has 24 references indexed in Scilit:
- Na+ transport by rabbit urinary bladder, a tight epitheliumThe Journal of Membrane Biology, 1976
- The sodium transport pool in toad urinary bladder epithelial cellsThe Journal of Membrane Biology, 1975
- Some effects of ouabain on cellular ions and water in epithelial cells of toad urinary bladderThe Journal of Membrane Biology, 1975
- Microelectrode studies of fundic gastric mucosa: Cellular coupling and shunt conductanceThe Journal of Membrane Biology, 1974
- Pathways for movement of ions and water across toad urinary bladderThe Journal of Membrane Biology, 1973
- The route of passive ion movement through the epithelium ofNecturus gallbladderThe Journal of Membrane Biology, 1972
- The thickness, composition and structure of some lipid bilayers and natural membranesThe Journal of Membrane Biology, 1971
- Uncoupling Cell Junctions in a Glandular Epithelium by Depolarizing CurrentScience, 1971
- Heaviside's “bessel cable” as an electric model for flat simple epithelial cells with low resistive junctional membranesJournal of Theoretical Biology, 1971
- Three-dimensional electrical field problems in physiologyProgress in Biophysics and Molecular Biology, 1970