|
Short-term NO Synthase Inhibition and the ATP
Affinity of Cardiac Na,K-ATPase
N. VRBJAR, M. STRNISKOVÁ, O. PECHÁŇOVÁ1, M.
GEROVÁ1
Institute for Heart Research and 1Institute of Normal and
Pathological Physiology, Slovak Academy of Sciences, Bratislava,
Slovak Republic
Received
October 17, 2001
Accepted March 20, 2002
Summary
It was previously shown that 4 hours´ lasting inhibition of
nitric oxide synthesis by administration of an L-arginine
analogue, the NG-nitro-L-arginine methyl ester (L-NAME) changed
the affinity of the Na-binding site of Na,K-ATPase thus
resulting in elevation of enzyme activity especially at higher
concentrations of sodium. Using the same experimental model, we
focused our attention in the present study to the question of
binding of ATP to the enzyme molecule in the left ventricle
(LV), ventricular septum (S) and the right ventricle (RV) of the
dog heart. Activation of the enzyme by increasing concentrations
of ATP revealed a significant increase of the Vmax only in
septum (by 38 %). The KM increased significantly in septum (by
40 %) and in left ventricle (by 56 %) indicating an altered
sensitivity of the ATP-binding site of Na,K-ATPase in the hearts
of NO-deficient animals. The alterations of Na,K-ATPase in its
ability to bind and hydrolyze ATP are localized to the tissue
surrounding the cavity of the left ventricle
Key
words
Sodium pump · Heart · Pressure overload · Nitric oxide · L-NAME
Reprint
requests
N. Vrbjar, Institute for Heart Research, Slovak Academy of
Sciences, Dúbravská cesta 9, 842 33 Bratislava, Slovak Republic.
Fax: +421 2 5477 6637, E-mail:
usrdnorb@savba.sk
|
