Reduced sodium pump alpha(1), alpha(3), and beta(1)-isoform protein levelsand Na+,K+-ATPase activity but unchanged Na+-Ca2+ exchanger protein levelsin human heart failure
Rhg. Schwinger et al., Reduced sodium pump alpha(1), alpha(3), and beta(1)-isoform protein levelsand Na+,K+-ATPase activity but unchanged Na+-Ca2+ exchanger protein levelsin human heart failure, CIRCULATION, 99(16), 1999, pp. 2105-2112
Citations number
35
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-Cardiac glycosides initiate an increase in force of contraction
by inhibiting the sarcolemmal sodium pump (Na+,K+-ATPase), thereby decreasi
ng Ca2+ extrusion by the Na+-Ca2+ exchanger, which increases the cellular c
ontent of Ca2+. In patients with heart failure the sensitivity toward cardi
ac glycosides is enhanced.
Methods and Results-Because the inotropic effect of cardiac glycosides may
be a function of the sodium pump and Na+-Ca2+ exchanger (NCE) expression le
vels, the present study aimed to investigate protein expression of both tra
nsporters (immunoblot with specific antibodies against the sodium pump cata
lytic alpha(1)-, alpha(2)-, alpha(3)-, and glycoprotein beta(1)-isoforms an
d against NCE) in left ventricle from failing (heart transplantations, New
York Heart Association class IV, n=21) compared with nonfailing (donor hear
ts, NF, n=22) human myocardium. The density of H-3-ouabain-binding sites (B
-max) and the Na+,K+-ATPase activity were also measured. In NYHA class IV,
protein levels of Na+,K+-ATPase alpha(1)- (0.62+/-0.06 of control), alpha(3
)- (0.70+/-0.09), and beta(1)- (0.61+/-0.04) but not alpha(2)-isoforms were
significantly reduced (P<0.01), whereas levels of NCE (0.92+/-0.13 of cont
rol) and calsequestrin (0.98+/-0.06) remained unchanged. Both Na+,K+-ATPase
activity (NF: 1.9+/-0.29; NYHA class IV: 1.1+/-0.17 mu mol ATP/min per mil
ligram of protein) and the H-3-ouabain binding sites (B-max NF: 15.9+/-1.9
pmol/mg protein; NYHA class IV: 9.7+/-1.5) were reduced in NYHA class IV an
d correlated significantly to each other (r(2)=0.73; P<0.0001), as did beta
(1)-subunit expression. In left ventricular papillary muscle strips from NY
HA class IV compared with nonfailing tissue the Na+-channel modulator BDF 9
198 exerted an increase in force of contraction with unchanged effectivenes
s but enhanced potency.
Conclusions-The enhanced sensitivity of failing human myocardium toward car
diac glycosides may be, at least in part, attributed to a reduced protein e
xpression and activity of the sarcolemmal Na+,K+-ATPase without a change in
Na+-Ca2+ exchanger protein expression.