Electrotonic Propagation of Kinin-Induced, Endothelium-Dependent Hyperpolarizations in Pig Coronary Smooth Muscles

Abstract

The kinins, substance P and bradykinin, cause endothelium-dependent hyperpolarizations in smooth muscles of the pig coronary artery. We tested whether the propagation, in the media, of these hyperpolarizations is passive or whether the hyperpolarizations are regenerated in the smooth muscle cells. The space constants measured in response to the kinin endothelium-dependent stimulations were compared to those obtained by electrical field stimulation. The space constant is 2.6 ± 0.2 mm (n = 13) measured for substance P and 2.2 ± 0.2 mm (n = 12) for bradykinin. The space constants established by electrical field stimulation-induced hyperpolarization are 3 ± 0.2 mm (n = 7) for strips with intact endothelium and 2.7 ± 0.3 mm (n = 7) for strips with removed endothelium. These results show that the space constants obtained for the kinin stimulations are not larger than those caused by electrical field stimulation. This suggests that the kinin-induced hyperpolarizations propagate, in the media, in a passive, electronic manner, therefore the hypothesis of regenerated kinin hyperpolarizations is unlikely.