title: The mitochondria-rich cell of frog skin as hormone-sensitive "shunt-path".
abstract: Further investigations about the role of the mitochondria-rich cell (MR cell) in hormone-mediated transport regulation in the epithelium of frog skin brought the following results: Unlike toad bladder, in frog skin the spontaneous potential difference cannot be reversed when Na transport is blocked. A similar situation is obtained when, in addition to transport-blockade, one applies a chemical gradient for chloride to the epithelium. Under these conditions we found that in the intact preparation as well as in the separated epithelium: (i) the reversed current (RC) is linearly related to the number of MR cells; (ii) RC is mainly carried by a passive, transcellular chloride flux inwards and (iii) RC is sensitive to nor-adrenaline (10(-7) M). The beta-blocker propranolol abolishes this effect. We propose that the MR cells are the sites of transepithelial shunt-path and that this chloride flux is transcellular. As it is hormone sensitive, it could be an important regulatory instrument for the regulation of overall salt transport (internal shorting).
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001001:Anura; D001693:Biological Transport, Active / Q000187:drug effects; D002021:Buffers; D002712:Chlorides / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011893:Rana esculenta; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012867:Skin / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D002021:Buffers; D002712:Chlorides; D011956:Receptors, Cell Surface; D000584:Amiloride; D009638:Norepinephrine