Activation of canonical transient receptor potential channels preserves Ca2+ entry and endothelium-derived hyperpolarizing factor–mediated function in vitro in porcine coronary endothelial cells and coronary arteries under conditions of hyperkalemia

Objectives Although membrane depolarization by hyperkalemia is known to reduce Ca2+ influx in endothelial cells, the mechanism by which endothelial Ca2+ channel is affected by hyperkalemia remains poorly studied. We studied the effect of hyperkalemia on canonical transient receptor potential channels, in particular canonical transient receptor potential channel 3, in modulation of endothelial intracellular Ca2+ concentration. Endothelium-derived hyperpolarizing factor–mediated function is Ca2+ dependent, and hyperkalemic cardioplegia/organ preservation solutions impair endothelium-derived hyperpolarizing factor–mediated function. We explored the role of canonical transient receptor potential channel 3 in endothelium-derived hyperpolarizing factor–mediated function and investigated whether modulation of these channels preserves endothelial Ca2+ influx and endothelium-derived hyperpolarizing factor–mediated function under the condition of hyperkalemic/cardioplegic exposure. Methods Intracellular Ca2+ concentration was measured with fluorescent dye in primary cultured porcine coronary endothelial cells exposed to hyperkalemic/cardioplegic solutions containing mild to extreme high K+ concentration. Endothelium-derived hyperpolarizing factor–mediated relaxation under hyperkalemic/cardioplegic exposure was studied in small porcine coronary arteries in a myograph in the presence of cyclooxygenase and nitric oxide synthase inhibitors and nitric oxide scavenger. Results Canonical transient receptor potential channel 3 blocker inhibited bradykinin-induced Ca2+ influx and attenuated endothelium-derived hyperpolarizing factor–mediated response. Hyperkalemic exposure inhibited canonical transient receptor potential channel 3–mediated Ca2+ influx in a K+ concentration-dependent manner (120 > 20 > 10 mmol/L). Ca2+ influx decreased in porcine coronary endothelial cells exposed to histidine-tryptophan-ketoglutarate, St Thomas' Hospital, and University of Wisconsin solutions that contained mild (10 mmol/L), moderate (20 mmol/L), and extreme high (125 mmol/L) K+ concentration, respectively. Canonical transient receptor potential channel activator prevented the reduction of Ca2+ influx in porcine coronary endothelial cells exposed to solutions containing mild to moderate high [K+ ]o and restored endothelium-derived hyperpolarizing factor–mediated response that was impaired by hyperkalemic exposure. Conclusions Canonical transient receptor potential channel 3 is involved in en