Key result
Angiotensin II increases intracellular pH recovery and induces AT1 receptor translocation in MDCK cells.
Why the study?
Does Angiotensin II affect intracellular pH recovery rate and AT1 receptor translocation in transfected MDCK cells?
Does Angiotensin II affect intracellular pH recovery rate and AT1 receptor translocation in transfected MDCK cells?
Answers are grounded in this paper and cite their sources.
In MDCK cells, the effect of Angiotensin II on NHE-1 activity is associated with ligand binding to the AT1 receptor and intracellular signaling events related to AT1 translocation.
The effect of ANG II on intracellular pH (pH(i)) recovery rate and AT(1) receptor translocation was investigated in transfected MDCK cells. The pH(i) recovery rate was evaluated by fluorescence microscopy using the fluorescent probe BCECF-AM. The human angiotensin II receptor isoform 1 (hAT(1)) translocation was analyzed by immunofluorescence and confocal microscope. Our data show that transfected cells in control situation have a pH(i) recovery rate of 0.219 +/- 0.017 pH U/min (n = 11). This value was similar to nontransfected cells [0.211 +/- 0.009 pH U/min (n = 12)]. Both values were significantly increased with ANG II (10(-9) M) but not with ANG II (10(-6) M). Losartan (10(-7) M) and dimethyl-BAPTA-AM (10(-7) M) decreased significantly the stimulatory effect of ANG II (10(-9) M) and induced an increase in Na(+)/H(+) exchanger 1 (NHE-1) activity with ANG II (10(-6) M). Immunofluorescence studies indicated that in control situation, the hAT(1) receptor was predominantly expressed in cytosol. However, it was translocated to plasma membrane with ANG II (10(-9) M) and internalized with ANG II (10(-6) M). Losartan (10(-7) M) induced hAT(1) translocation to plasma membrane in all studied groups. Dimethyl-BAPTA-AM (10(-7) M) did not change the effect of ANG II (10(-9) M) on the hAT(1) receptor distribution but induced its accumulation at plasma membrane in cells treated with ANG II (10(-6) M). With ionomycin (10(-6) M), the receptor was accumulated in cytosol. The results indicate that, in MDCK cells, the effect of ANG II on NHE-1 activity is associated with ligand binding to AT(1) receptor and intracellular signaling events related to AT(1) translocation.
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Thieme et al. (2008) studied this question. Angiotensin II vs. Control was evaluated on intracellular pH recovery rate. In MDCK cells, Angiotensin II (10^-9 M) significantly increased the intracellular pH recovery rate compared to control (0.219 pH U/min) and induced AT1 receptor translocation to the plasma membrane.
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