Prolonged effects of acute gamma irradiation on acetylcholine-induced potassium currents in human umbilical vein endothelial cells

We have recently reported an acute effect BE gamma irradiation (15 Gy, 1 Gy /min) on acetylcholine-mediated endothelium-dependent relaxation in rat aor tic rings. Given the importance of permeability to K+ to endothelium-depend ent relaxation, we have evaluated the effect of the same radiation on K+ cu rrents in human endothelial cells in culture using the patch-clamp techniqu e in the whole-cell recording configuration. Our results indicate that, in resting cells, gamma irradiation has no effect on endothelial permeability to K+. However, irradiation during stimulation of endothelial cells with ac etylcholine reduces the sustained increase in permeability to K+ observed i n the acetylcholine-stimulated, nonirradiated cells, Additional experiments using K+ channel inhibitors (TEA, charybdotoxin, apamin) suggest that irra diation mag. in part decrease the prolonged activation of Ca2+-activated K channels by acetylcholine. Taken together with our previous finding that i rradiation inhibits the acute relaxing effects of acetylcholine, these resu lts show that gamma irradiation also affects the delayed effects of acetylc holine on permeability to K+. (C) 2001 by Radiation Research Society.