Am. J. Respir. Cell Mol. Biol., Volume 25, Number 3, September, 2001 285-290

Basic Electrical Properties of In situ Endothelial Cells of Small Pulmonary Arteries during Postnatal Development

Andrea Olschewski, Horst Olschewski, Michael E. Bräu, Gunter Hempelmann, Werner Vogel, and Boris V. Safronov

Department of Anesthesiology and Intensive Care Medicine; Department of Internal Medicine; Department of Physiology, Justus-Liebig-University, Giessen, Germany; and Instituto de Biologia Molecular e Celular, Porto, Portugal

Small pulmonary arteries are the major determinants of pulmonary artery pressure and vascular resistance. Their endothelium modulates pulmonary resistance, remodeling, and blood fluidity. We developed a method that provides access to the luminal surface of small pulmonary arteries of rat and allows the patch-clamp study of electrical properties of in situ endothelium. At birth, the membrane was predominantly permeable for K⁺, showing a resting potential of 70 mV. This conductance was not voltage-dependent and was insensitive to standard blockers of K⁺ channels such as tetraethylammonium, charybdotoxin, and 4-aminopyridine. The first 22 d of development were accompanied by an additional expression of a Cl conductance, increasing membrane potential to 45 mV. Acidosis reduced K⁺ conductance and depolarized the membrane, whereas alkalosis resulted in hyperpolarization. Two-electrode recordings revealed tight electrical coupling (83%) between neighboring cells in the circumferential direction of the artery. The electrotonic length constant for endothelium was 13.3 µm, indicating that most cells in one cross section of a small artery are well coupled. Thus, the resting membrane conductances in small pulmonary artery endothelial cells change with postnatal development and are modulated by pH.