Heart failure can be caused by pro-hypertrophic humoral factors such as
angiotensin II (Ang II), which regulates
protein kinase activities. The intermingled responses of these
kinases lead to the early compensated
cardiac hypertrophy, but later to the uncompensated phase of
heart failure. We have shown that although beneficial,
cardiac hypertrophy is associated with modifications in
ion channels that are mainly mediated through
mitogen-activated
protein (MAP)
kinase and
phosphatidylinositol 3-kinase (PI3K) activation. This study evaluates the control of L-type Ca(2+) current (I(Ca,L)) by the Ang II/PI3K pathway in hypertrophied ventricular myocytes from volume-overload rats using the perforated patch-clamp technique. To assess activation of the I(Ca,L) in cardiomyocytes, voltages of 350 ms in 10 mV increments from a holding potential of -85 mV were applied to cardiocytes, with a pre-pulse to -45 mV for 300 ms. Volume overload-induced
hypertrophy reduces I(Ca,L), whereas addition of Ang II alleviates the hypertrophic-induced decrease in a PI3K-dependent manner. Acute administration of Ang II (10(-6) mol/L) to normal adult cardiomyocytes had no effect; however,
captopril reduced their basal I(Ca,L). In parallel,
captopril regressed the
hypertrophy and inverted the Ang II effect on I(Ca,L) seemingly through a PI3K upstream effector. Thus, it seems that regression of
cardiac hypertrophy by
captopril improved I(Ca,L) partly through PI3K.