Intracellular ion concentrations in the isolated frog skin epithelium: Evidence for different types of mitochondria-rich cells

Summary 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 × 10^–6m, innerbath) 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^–4m, 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 abasal 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.I wish to thank Cathy Langford, Cindy Partain, and Ray Whitfield for their excellent technical assistance. Financial support was provided by NIH grants DK35717 and 1S10-RR0-234501.