Browsing by Subject "Kidney Tubules, Distal"

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    Characterization of the ion transport responses to ADH in the MDCK-C7 cell line
    (2000-03) Lahr, Thomas F.; Record, Rae D.; Hoover, Diane K.; Hughes, Cynthia L.; Blazer-Yost, Bonnie
    The Madin-Darby canine kidney (MDCK) cell line expresses many characteristics of the renal collecting duct. The MDCK-C7 subclone forms a high-resistance, hormone-responsive model of the principal cells, which are found in distal sections of the renal tubule. The electrophysiological technique of short-circuit current measurement was used to examine the response to antidiuretic hormone (ADH) in the MDCK-C7 clone. Three discrete electrogenic ion transport phenomena can be distinguished temporally and by the use of inhibitors and effectors. Initially the cells exhibit anion secretion through the cystic fibrosis transmembrane conductance regulator (CFTR). The presence of CFTR was confirmed by immunoprecipitation followed by Western blotting. The CFTR-mediated anion secretion is transient and is followed, in time, by a verapamil- and Ba(+)-sensitive anion secretion or cation absorption and, finally, by Na+ reabsorption via epithelial Na+ channels (ENaC). In contrast to other studies of MDCK cells, we see no indication that the presence of CFTR functionally inhibits ENaC. The characterization of the various ion transport phenomena substantiates this cell line as a model renal epithelium that can be used to study the hormonal and metabolic regulation of ion transport.
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    Sex differences in proximal and distal nephron function contribute to the mechanism of idiopathic hypercalcuria in calcium stone formers
    (American Physiological Society, 2015-07-01) Ko, Benjamin; Bergsland, Kristin; Gillen, Daniel L.; Evan, Andrew P.; Clark, Daniel L.; Baylock, Jaime; Coe, Fredric L.; Worcester, Elaine M.; Department of Anatomy & Cell Biology, IU School of Medicine
    Idiopathic hypercalciuria (IH) is a common familial trait among patients with calcium nephrolithiasis. Previously, we have demonstrated that hypercalciuria is primarily due to reduced renal proximal and distal tubule calcium reabsorption. Here, using measurements of the clearances of sodium, calcium, and endogenous lithium taken from the General Clinical Research Center, we test the hypothesis that patterns of segmental nephron tubule calcium reabsorption differ between the sexes in IH and normal subjects. When the sexes are compared, we reconfirm the reduced proximal and distal calcium reabsorption. In IH women, distal nephron calcium reabsorption is decreased compared to normal women. In IH men, proximal tubule calcium reabsorption falls significantly, with a more modest reduction in distal calcium reabsorption compared to normal men. Additionally, we demonstrate that male IH patients have lower systolic blood pressures than normal males. We conclude that women and men differ in the way they produce the hypercalciuria of IH, with females reducing distal reabsorption and males primarily reducing proximal tubule function.