Cellular electrophysiologic abnormalities occurring during the remodeling of the infarcted heart may lead to fatal arrhythmias. The pacemaker current If is consistently overexpressed in left ventricular myocytes from hypertrophied rat and failing human hearts. However its occurrence and properties in post myocardial infarction (PMI) hearts has not been characterized. The aim of this study was to evaluate If expression in ventricular myocytes isolated from areas close and remote to the scar, i.e. left (LVM) and right (RVM) ventricular myocytes of PMI rats 6 months alter coronary ligation. The heart weight to body weight ratio was (mean±s.e.m.) 5.1±0.7 mg/g; the membrane capacitance was 293±13 pF in LVM (n=52) and 229±10 pF in RVM (n=43, p<0.05). Cells were superfused with a modified Tyrode's solution also containing (mM): KCI 25, BaCI2 2, MnCI2 2, 4-aminopymlrne 0.5 to amplify If and reduce overlapping currents. From a holding potential of -40 mV, a time-dependent, cesium-sensitive inward current could be elicited by hyperpolarization in 100% LVM and in 82% RVM. Activation curve was sigmoidal, with a midpoint of -96±2 mV in LVM and -97±2 mV in RVM (n=20. n.s.). Also the reversal potentral (Vrev) of If was similar: -16±2 mV in LVM and -19±2 mV in RVM (n= 8 n.s.). Typically, Vrev was shifted to more negative potentials by reducing extracellular K+ to 54 mM (by 13±3 mV, n=3) or Na+ to 35 mM (by 11 ± 1 mV, n=3). Maximum specific conductance was significantly higher in LVM (25±3 pS/pF, n=40) than in RVM (15+3 pS/pF, n=34) (p<0.05). In LVM from control rats, If occurred with a very low amplitude: its activatron midpoint was -100±2 mV and maximal conductance 4.5±1.8 pS/pF (n=4). Thus, If is significantly enhanced in ventricular myocytes from PMI rat hearts, its expression and density appear to be higher in regions closer to the scar.
|Titolo:||Properties of the pacemaker current If in rat ventricular myocytes isolated from chronic infarcted hearts.|
|Anno di registrazione:||2000|
|Autori di Ateneo:|
|Autori:||A. MUGELLI; L. SARTIANI; P. DE PAOLI; E. CERBAI; F. AIMOND; G. VASSORT|
|Appare nelle tipologie:||1c - Abstract su rivista|
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