Endothelial cells freshly isolated from resistance-sized pulmonary arteries possess a unique K+ current profile

We have, for the first time, developed a reliable method for freshly isolat ing viable endothelial cells from resistance-sized rat pulmonary arteries. The endothelial origin of these cells was confirmed using indirect immunofl uorescence, utilizing fluorescently labeled low-density lipoprotein. Biophy sical and pharmacological patch-clamp experiments conducted under quasiphys iological cationic gradients revealed that these cells had a mean resting m embrane potential of similar to-38 mV and displayed a delayed-rectifying K current. Immunohistochemical staining of rat lung cross-sections revealed an abundance of K(v)1.5 channel protein in pulmonary endothelium. This is t he first report of a delayed-rectifying K+ current in endothelial cells of resistance-sized pulmonary arteries. Since changes in membrane potential as sociated with K+ channel activity affect release of vasoactive substances f rom endothelial cells, this finding has important implications for understa nding the mechanisms underlying control of pulmonary vascular tone. (C) 199 9 Academic Press.