Intracellular Ca2+ and PKC activation do not inhibit Na+ and water transport in rat CCD.

Academic Article

Abstract

  • Experiments examined the effects of elevation of intracellular calcium concentration ([Ca2+]i) or activation of protein kinase C (PKC) on Na+ and water transport in the rat cortical collecting duct (CCD). We measured the lumen-to-bath 22Na+ flux (J1-->b), transepithelial voltage (VT), and water permeability (Pf) in CCD from deoxycorticosterone (DOC)-treated rats. Ionomycin (0.5 and 1 microM) and thapsigargin (1 and 2 microM) were used to increase [Ca2+]i. Phorbol 12-myristate 13-acetate (PMA; 0.3 and 1 microM) and oleoyl-acetyl-glycerol (OAG; 100 microM) were used as activators of PKC. [Ca2+]i was measured in isolated perfused tubules using the fluorescent dye fura 2. When added to the bathing solution, 220 pM arginine vasopressin (AVP) failed to affect [Ca2+]i, whereas 1 microM ionomycin increased [Ca2+]i by 103 +/- 15% and 2 microM thapsigargin increased [Ca2+]i by 24 +/- 4%. In flux studies, neither ionomycin nor thapsigargin affected J1-->b or Pf, although ionomycin caused marked morphological changes. Ionomycin also failed to alter either parameter in tubules from non-DOC-treated rats. Neither 100 microM OAG nor 1 microM PMA affected J1-->b or Pf. OAG at 50 microM had no effect on VT or transepithelial resistance, indicating no inhibition of conductive Na+ transport. We conclude that increased [Ca2+]i and PKC activation do not affect J1--b or Pf in the rat CCD. These findings may account for the sustained increase in J1--b produced in the rat CCD by AVP.
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    Keywords

  • Animals, Arginine Vasopressin, Biological Transport, Calcium, Enzyme Activation, In Vitro Techniques, Intracellular Membranes, Kidney Cortex, Kidney Tubules, Collecting, Male, Perfusion, Protein Kinase C, Rats, Rats, Sprague-Dawley, Sodium, Water
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    Author List

  • Rouch AJ; Chen L; Kudo LH; Bell PD; Fowler BC; Corbitt BD; Schafer JA
  • Start Page

  • F569
  • End Page

  • F577
  • Volume

  • 265
  • Issue

  • 4 Pt 2