Heart failure (HF) was induced by
ligation of the left anterior descending artery (LAD). Left ventricular end-diastolic pressure (LVEDP) >25 mmHg (at day 23 after LAD
ligation) was the inclusion criterion. The rats were divided into three groups:
sham-operated (
Sham, n = 23, LVEDP: 5.6 +/- 0.6 mmHg), HF (n = 14, LVEDP: 29.4 +/- 1.4 mmHg), and
candesartan (1 mg.kg(-1).day(-1) sc)-treated HF (HF + Can, n = 9, LVEDP: 29.2 +/- 1.2 mmHg). After 7 days (i.e., 29 days after LAD
ligation) semiquantitative immunoblotting revealed increased abundance of inner medulla
aquaporin-2 (AQP2) and AQP2 phosphorylated at Ser(256) (p-AQP2) in HF. There was also markedly enhanced apical targeting of AQP2 and p-AQP2 in inner medullary collecting duct (IMCD) in HF compared with
Sham rats, shown by immunocytochemistry.
Candesartan treatment significantly reversed the increases in both AQP2 and p-AQP2 expression and targeting. In contrast, there were only modest changes in other collecting duct segments. Semiquantitative immunoblots revealed increased expression of type 3
Na(+)/H(+) exchanger (NHE3) and Na(+)-K(+)-2Cl(-)
cotransporter (NKCC2) in kidneys from HF compared with
Sham rats: both effects were reversed or prevented by
candesartan treatment. The
protein abundance of alpha-
epithelial sodium channel (alpha-ENaC) was increased while beta-ENaC and gamma-ENaC expression was decreased in the cortex and outer stripe of the outer medulla in HF compared with
Sham rats, which was partially reversed by
candesartan treatment. These findings strongly support an important role of
angiotensin II in the pathophysiology of renal water and
sodium retention associated with HF.