Signaling pathways in the biphasic effect of ANG II on Na+/H+ exchanger in T84 cells.
The effect of ANG II on pH(i), [Ca(2+)](i) and cell volume was investigated in T84 cells, a cell line originated from colon epithelium, using the probes BCECF-AM, Fluo 4-AM and acridine orange, respectively. The recovery rate of pH(i) via the Na(+)/H(+) exchanger was examined in the first 2 min following the acidification of pH(i) with a NH(4)Cl pulse. In the control situation, the pH(i) recovery rate was 0.118 +/- 0.001 (n = 52) pH units/min and ANG II (10(-12) M or 10(-9) M) increased this value (by 106% or 32%, respectively) but ANG II (10(-7) M) decreased it to 47%. The control [Ca(2+)](i) was 99 +/- 4 (n = 45) nM and ANG II increased this value in a dose-dependent manner. The ANG II effects on cell volume were minor and late and should not interfere in the measurements of pH(i) recovery and [Ca(2+)](i). To document the signaling pathways in the hormonal effects we used: Staurosporine (a PKC inhibitor), W13 (a calcium-dependent calmodulin antagonist), H89 (a PKA inhibitor) or Econazole (an inhibitor of cytochrome P450 epoxygenase). Our results indicate that the biphasic effect of ANG II on Na(+)/H(+) exchanger is a cAMP-independent mechanism and is the result of: 1) stimulation of the exchanger by PKC signaling pathway activation (at 10(-12) - 10(-7) M ANG II) and by increases of [Ca(2+)](i) in the lower range (at 10(-12) M ANG II) and 2) inhibition of the exchanger at high [Ca(2+)](i) levels (at 10(-9) - 10(-7) M ANG II) through cytochrome P450 epoxygenase-dependent metabolites of the arachidonic acid signaling pathway.
Musa-Aziz
R
R
Department of Physiology and Biophysics, Instituto de Ciências Biomédicas, University of São Paulo, São Paulo 05508-900, Brazil.
Oliveira-Souza
M
M
Mello-Aires
M
M
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D048429:Cell Size / Q000187:drug effects*; D003106:Colon / Q000187:drug effects* / Q000378:metabolism; D003110:Colonic Neoplasms; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007546:Isoquinolines / Q000494:pharmacology; D019808:Losartan / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology
D007546:Isoquinolines; D017923:Sodium-Hydrogen Exchangers; D013449:Sulfonamides; D000804:Angiotensin II; C057360:5-(N,N-hexamethylene)amiloride; D000584:Amiloride; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; D019311:Staurosporine; D019808:Losartan; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium