Endothelial cells freshly isolated from small pulmonary arteries of the rat possess multiple distinct k+ current...

This study demonstrates for the first time that endothelial cells freshly isolated from small pulmonary arteries of the rat, based on their electrophysiological profile, possess two distinct populations of cells. Immunohistochemical staining revealed the presence of both anti-Kv1.5 and anti-Kir2.1 immunoreactivity in the endothelium of small pulmonary arteries. Patch-clamp studies demonstrated that 90% of cells studied exhibited an electrophysiological profile that was characterized by a delayed rectifier K+ conductance. However, the remaining 10% of cells studied showed the complete absence of a delayed rectifier K+ current and were characterized by an inward rectifier K+ conductance. Together these results indicate that endothelial cells isolated from rat small pulmonary arteries possess a heterogeneous population of cells that may be distinguished by their markedly different electrophysiological profiles. These different populations of cells may differ in their control of the resting membrane potential of endothelial cells, and thereby altering Ca2+ homeostasis and release of vasoactive compounds. These findings may therefore have important implications for understanding the regulation of pulmonary vascular tone.