Intracellular Ca2+ and PKC activation do not inhibit Na+ and water transport in rat CCD.
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.
Rouch
A J
AJ
Department of Physiology and Biophysics, University of Alabama at Birmingham 35294.
Chen
L
L
Kudo
L H
LH
Bell
P D
PD
Fowler
B C
BC
Corbitt
B D
BD
Schafer
J A
JA
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008297:Male; D010477:Perfusion; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000493:pharmacokinetics*; D014867:Water / Q000378:metabolism*
D014867:Water; D001127:Arginine Vasopressin; D012964:Sodium; D011493:Protein Kinase C; D002118:Calcium