On the distribution of Na+ pump sites in the frog skin
Open Access
- 1 December 1977
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 75 (3) , 968-973
- https://doi.org/10.1083/jcb.75.3.968
Abstract
Exposure of the outside of the isolated frog skin to a Ringer''s solution, made hypertonic by the addition of mannitol, causes a rapid and sustained increase in transepithelial permeability through a structural distortion-a focal blistering-of the tight junctions of the outermost living cell layer. [3H]ouabain, used as an autoradiographic marker for the Na+-pump (Na+-K+-ATPase), is usually unable to penetrate the frog skin from the outside solution, but when added to a hypertonic mannitol-Ringer''s solution in the outside bath it readily penetrates the epithelium, presumably through the opened shunt pathway. Radioautographic analysis of [3H]ouabain binding sites revealed that most of the ouabain that enters from the outside solution binds to sites on the cell membranes of the stratum spinosum, as was the case when it was applied from the inside bath in an earlier study. The outer living cell layer, the 1st to be exposed to ouabain, does not appear to be the major site for the Na+-pump and is not likely to be responsible for most of the active pumping of Na+. This result demonstrates that previous failure to show a high density of Na+-pump sites on the cells of the outermost layer, when [3H]ouabain was applied from the inside solution, was not due to the inability of the marker to reach these cells at a sufficient concentration to reveal all the pump sites. These results provide support for a model of Na+-transport across the frog skin which distributes the active pump step on the inward facing membranes of all the living cells.This publication has 11 references indexed in Scilit:
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