An If-like current was present in 93% of ventricular myocytes from old hypertensive rats compared to 12.1% from young rats (P<0.01), which may favor spontaneous action potentials.
An If-like current is significantly upregulated in ventricular myocytes from old spontaneously hypertensive rats, which may contribute to the occurrence of spontaneous action potentials and arrhythmogenesis in hypertensive heart disease.
Absolute Event Rate: 93% vs 12.1%
p-value: p=< 0.01
Left ventricular myocytes isolated from the heart of young (2-month-old) and old (18- to 20-month-old) spontaneously hypertensive rats (SHRs) were studied in the whole-cell configuration. Since multicellular preparations from old SHRs show a diastolic depolarization phase, we performed experiments to test whether it was associated with the presence of a hyperpolarization-activated If-like current. 2. In control Tyrode solution, a time-dependent increasing inward current activated by hyperpolarization was recorded in myocytes from old SHRs showing a diastolic depolarization phase. A barium-insensitive, caesium-sensitive, time-dependent inward current was recorded in a minority (4 of 33) of cells from young SHRs (membrane capacitance, 160 +/- 7 pF) but in 93% (25 of 27, P < 0.01) of myocytes from old SHRs (membrane capacitance, 355 +/- 19 pF, P < 0.01). 3. The current was fully activated at -120 mV and voltage of half-maximal activation was -88.1 +/- 1.5 mV; it was blocked by extracellular CsCl (4 mM) in a voltage-dependent manner. Reducing K+o from 25 to 5.4 mM caused a shift of the reversal potential from -17.3 +/- 3.8 to -25.7 +/- 2.7 mV and a 60% decrease of current conductance. 4. These findings suggest that an If-like current is present in rat ventricular myocytes from old SHRs, where it might favour the occurrence of spontaneous action potentials.
Cerbai et al. (Thu,) conducted a other in Hypertension (Spontaneously hypertensive rats) (n=60). Old age (18- to 20-month-old) vs. Young age (2-month-old) was evaluated on Presence of a barium-insensitive, caesium-sensitive, time-dependent inward current (If-like current) (p=< 0.01). An If-like current was present in 93% of ventricular myocytes from old hypertensive rats compared to 12.1% from young rats (P<0.01), which may favor spontaneous action potentials.