Intracellular ion concentrations in the isolated frog skin epithelium: evidence for different types of mitochondria-rich cells.
Intracellular ion concentrations were determined in split skins of Rana pipiens using the technique of electron microprobe analysis. Under control conditions, principal cells and mitochondria-rich cells (MR cells) had a similar intracellular ion composition, only the Cl concentration in MR cells was significantly lower. Inhibition of transepithelial Na transport by low concentrations of ouabain (2 x 10(-6) M, inner bath) resulted in a Na concentration increase of principal cells from 10.9 to 54.3 mmol/kg wet wt. The increase was completely abolished by simultaneous application of amiloride (10(-4) M, outer bath). Amiloride alone resulted in a significant decrease of the Na concentration to 6.1 mmol/kg. w.w. Among MR cells, two different groups of cells could be distinguished; cells that showed a Na increase after ouabain which was even larger than that in principal cells and cells that did not respond to ouabain. In about half of all ouabain-sensitive MR cells the Na increase could be prevented by amiloride. According to these results, a subpopulation of MR cells displays the transport characteristics expected for a transepithelial Na transport compartment, an apical amiloride-sensitive Na influx and a basal ouabain-inhibitable Na efflux. Given the small number of cells, however, it is unlikely that this subtype of MR cells contributes significantly to the overall rate of transepithelial Na transport.
Rick
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Department of Physiology and Biophysics, University of Alabama, Birmingham.
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism / Q000648:ultrastructure; D007424:Intracellular Fluid / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D010042:Ouabain / Q000494:pharmacology; D011894:Rana pipiens; D012867:Skin / Q000378:metabolism* / Q000648:ultrastructure; D012964:Sodium / Q000378:metabolism
D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D008274:Magnesium; D002118:Calcium