Testosterone rapidly increases Ca²⁺-activated K⁺currents causing hyperpolarization in human coronary artery endothelial cells

Abstract

© 2017 Elsevier Ltd Testosterone has endothelium-dependent vasodilatory effects on the coronary artery, with some reports suggesting endothelial ion channel involvement. This study employed the whole-cell patch clamp technique to investigate the effect of testosterone on ion channels in human coronary artery endothelial cells (HCAECs) and the mechanisms involved. We found that 0.03–3 μM testosterone significantly induced a rapid, concentration-dependent increase in total HCAEC current (EC50, 71.96 ± 1.66 nM; maximum increase, 59.13 ± 8.37%; mean ± SEM). The testosterone-enhanced currents consisted of small- and large-conductance Ca2+-activated K+currents (SKCaand BKCacurrents), but not Cl−and nonselective cation currents. Either a non-permeant testosterone conjugate or the non-aromatizable androgen dihydrotestosterone (DHT) could increase HCAEC currents as well. The androgen receptor antagonist flutamide prevented this testosterone, testosterone conjugate, and DHT effect, while the estrogen receptor antagonist fulvestrant did not. Incubating HCAECs with pertussis toxin or protein kinase A inhibitor H-89 largely inhibited the testosterone effect, while pre-incubation with phospholipase C inhibitor U-73122, prostacyclin inhibitor indomethacin, nitric oxide synthase inhibitor L-NAME or cytochrome P450 inhibitor MS-PPOH, did not. Finally, testosterone application induced HCAEC hyperpolarization within minutes; this effect was prevented by SKCaand BKCacurrent inhibitors apamin and iberiotoxin. This is the first electrophysiological demonstration of androgen-induced KCacurrent increase, leading to hyperpolarization, in any endothelial cell, and the first report of SKCaas a testosterone target. Our data show that testosterone rapidly increased whole-cell HCAEC SKCaand BKCacurrents via a surface androgen receptor, Gi/oprotein, and protein kinase A. This mechanism may explain rapid testosterone-induced coronary vasodilation seen in vivo.