TITLE:
ANP impairs the dose-dependent stimulatory effect of ANG II or AVP on H+-ATPase subcellular vesicle trafficking
AUTHORS:
M. Oliveira-Souza, P. Morethson, G. Malnic, M. Mello-Aires
KEYWORDS:
H+-ATPase Vesicle Trafficking; ANP; ANG II; AVP
JOURNAL NAME:
Open Journal of Molecular and Integrative Physiology,
Vol.3 No.3,
August
26,
2013
ABSTRACT:
The
effect of angiotensin II (ANG II) or arginine vasopressin (AVP) alone or plus
atrial natriuretic peptide (ANP) on H+-ATPase subcellular vesicle
trafficking was investigated in MDCK cells following intracellular pH (pHi)
acidification by exposure to20 mMNH4Cl for 2 min in a Na+-free solution containing
Schering 28080, conditions under which H+-AT-Pase is the only cell
mechanism for pHi recovery. Using the acridine orange fluorescent probe (5mM) and confocal microscopy, the
vesicle movement was quantified by determining, for each experimental group,
the mean slope of the line indicating the changes in apical/basolateral
fluorescence density ratio over time during the first 5.30 min of the pHi
recovery period. Under the control conditions, the mean slope was 0.079 ± 0.0033 min-1 (14) and it increased
significantly with ANG II [10-12 and 10-7 M, respectively to 0.322 ± 0.038 min-1 (13) and 0.578 ± 0.061 min-1 (12)] or AVP [10-12 and 10-6 M,
respectively to 0.301 ± 0.018 min-1 (12) and
0.687 ± 0.049 min-1 (11)]. However, in presence of ANP (10-6 M, decreases cytosolic free calcium),
dimethyl-BAPTA/AM (5 × 10-5 M, chelates intracellular calcium) or
colchicine (10-5 M, 2-h
preincubation; inhibits microtubule-dependent vesicular trafficking) alone or
plus ANG II or AVP the mean slopes were similar to the control values, indicating
that such agents blocked the stimulatory effect of ANG II or AVP on vesicle
trafficking. The results suggest that the pathway responsible for the increase
in cytosolic free calcium and the microtu-bule-dependent vesicular
trafficking are involved in this hormonal stimulating effect. Whether
cytosolic free calcium reduction represents an important direct mechanism for
ANP impairs the dose-dependent stimulatory effect of ANG II or AVP on H+-ATPase subcellular
vesicle trafficking, or is a side effect of other signaling pathways which will
require additional studies.