Action of ANG II and ANP on colon epithelial cells.
The interaction of angiotensin II (ANG II) and atrial natriuretic peptide (ANP) on intracellular pH (pH(i)) and calcium ([Ca2+](i)) was investigated in T84 cells (a permanent cell line derived from human colon epithelium) using the fluorescent stains BCECF/AM and Fluo 4/AM, respectively. pH(i) recovery rate mediated by the Na(+)/H+ exchanger (NHE) was examined following an NH4Cl pulse. Under control conditions pH(i) recovered at 0.114+/-0.005 pH units/min (n=35). ANG II (10(-12) or 10(-9) M) increased this value, whilst ANG II (10(-7) M) decreased it. These effects of ANG II were impaired by simultaneous addition of 1 microM or 25 microM HOE-694, indicating that the stimulatory and inhibitory effects of ANG II on pH(i) recovery are mediated in part via the NHE1 and NHE2 isoforms. ANG II increased [Ca2+]i concentration-dependently. ANP (10(-6) M) or dimethyl-BAPTA/AM (50 microM) blocked the effects of ANG II on [Ca2+]i and on the rate of pH(i) recovery. Thapsigargin (10(-5) M) enhanced the effect of ANG II on [Ca2+]i and reversed its stimulatory effect on the rate of pH(i) recovery to an inhibitory one. External Ca(2+)-free solution did not affect the effects of ANG II on these parameters. These data suggest that the [Ca2+]i increase induced by ANG II is dependent on intracellular calcium stores. They are compatible with the demonstration of two sites on the C-terminal of the Na(+)/H+ exchanger, one stimulating Na(+)/H+ activity by increases of [Ca2+]i in the lower range (at 10(-12) or 10(-9) M ANG II) and the other inhibiting this activity at high [Ca2+]i levels (at 10(-7) M ANG II). ANP or dimethyl-BAPTA/AM, by impairing the pathway mediating the increase in [Ca2+]i, block both the stimulatory and inhibitory effects of ANG II.
Musa-Aziz
Raif
R
Department of Physiology and Biophysics, Instituto de Ciências Biomédicas University of São Paulo, SP, 05508-900, Brazil. mmaires@fisio.icb.usp.br
Mello-Aires
Margarida
M
D000804:Angiotensin II / Q000494:pharmacology*; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D003106:Colon / Q000166:cytology / Q000187:drug effects; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000166:cytology* / Q000187:drug effects; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism; D013450:Sulfones / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
C460021:5,5'-dimethyl bis(o-aminophenoxy)ethane-N,N,N',N' tetraacetic acetoxymethyl ester; D006146:Guanidines; C081517:SLC9A2 protein, human; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C069139:growth factor-activatable Na-H exchanger NHE-1; D000804:Angiotensin II; C074107:3-methylsulfonyl-4-piperidinobenzoyl guanidine; D004533:Egtazic Acid; D019284:Thapsigargin; D009320:Atrial Natriuretic Factor; D002118:Calcium