Intracellular angiotensin (1-7) increases the inward calcium current in cardiomyocytes. On the role of PKA activation.

The influence of intracellular administration of angiotensin (1-7) (Ang 1-7) on the inward calcium current was investigated in myocytes isolated from the left ventricle of Wistar Kyoto rat hearts using the patch-clamp technique. The results indicated: (1) the intracellular administration of Ang (1-7) (100 nM) enhanced the peak inward calcium current (I Ca); (2) the intracellular administration of A779 (100 nM) which a Mas receptor inhibitor, abolished the effect of Ang (1-7) on the calcium current; (3) the activation of PKA and consequent phosphorylation of calcium channels seems to be the mechanism involved in the increment of calcium current induced by the heptapeptide because the intracellular dialysis of the PKA inhibitor suppressed the effect of the heptapeptide; (4) the effect of Ang (1-7) was not related to its secretion into the extracellular space; (5)intracellular dialysis of Ang II (100 nM) has an opposite effect and reduced the peak I Ca; (6) extracellular administration of Ang II (100 nM) to cells previously dialyzed with Ang (1-7) also reduced the peak I Ca previously enhanced by Ang (1-7); and (7) intracellular Ang (1-7) reduced the heart cell volume. Implications for heart contractility were discussed.