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- Title
Action of ANG II and ANP on colon epithelial cells.
- Authors
Musa-Aziz, Raif; Mello-Aires, Margarida
- Abstract
The interaction of angiotensin II (ANG II) and atrial natriuretic peptide (ANP) on intracellular pH (pHi) 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. pHi recovery rate mediated by the Na+/H+ exchanger (NHE) was examined following an NH4Cl pulse. Under control conditions pHi 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 μM or 25 μM HOE-694, indicating that the stimulatory and inhibitory effects of ANG II on pHi 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 μM) blocked the effects of ANG II on [Ca2+]i and on the rate of pHi recovery. Thapsigargin (10−5 M) enhanced the effect of ANG II on [Ca2+]i and reversed its stimulatory effect on the rate of pHi recovery to an inhibitory one. External Ca2+-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.
- Subjects
ANGIOTENSIN II; ATRIAL natriuretic peptides; HEART atrium; PEPTIDE hormones; CELL lines; EPITHELIAL cells
- Publication
Pflügers Archiv: European Journal of Physiology, 2005, Vol 450, Issue 6, p405
- ISSN
0031-6768
- Publication type
Article
- DOI
10.1007/s00424-005-1459-6