Effect of Nonconventional Beta-adrenoceptor Agonist CGP 12177 on L-type Calcium Current and Contraction Force in Human Myocardium
Abstract
The aim of this study was to evaluate the effect of CGP 12177, a nonconventional partial agonist of β-adrenoceptors, on the Ltype
Ca2+ current (ICa) in whole-cell patch-clamped atrial myocytes and the contraction force of the atrial trabeculae from failing human heart.
It was established that CGP 12177 stimulated ICa in a dose-dependent manner and the maximal effect was obtained with a 1-mmol/l
concentration. In 14 atrial cells, ICa increased from 309.0±49.4 pA at control to 549.5±95.9 pA at 1-mmol/l CGP 12177 (n=14) (p<0.05). This
represented an increase in Ca2+-current density (ICa/membrane capacitance) from 2.38±0.26 pA/pF to 4.07±0.54 pA/pF (n=14). The concentration
of agonist required to produce 50 percent of the maximal increase of ICa (EC50) was 0.016±0.007 μmol/l (n=14). ICa density under the
influence of 1-mmol/l isoprenaline was 6.78±1.07 pA/pF (n=5), i.e. more than twofold that documented with stimulation by CGP12177
(p<0.05). These data confirm that CGP12177 is a partial β-adrenoceptors agonist. The concentration of CGP 12177 that induced the maximal
increase of ICa, i.e. 1 μmol/l, evoked an increase of contraction force 111.66±4.34 percent (n=6) as compared with its level at control conditions.
Our data show that the nonconventional partial agonist CGP 12177 increases the L-type Ca2+ current in isolated atrial cells and the contraction
force of atrial trabeculae from failing human heart. Finally, we provide a discussion on to which type of b-adrenoceptors the effect of CGP
12177 on the L-type Ca2+ current and contraction force might be attributed.
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