Multiple Ionic Mechanisms Activated by Bradykinin in Coronary Venular Endothelial Cells

Abstract

In coronary endothelium, bradykinin (BK) modulates production of vasodilators by stimulating Ca2+ influx. To examine the ionic currents involved in this process, we applied BK (100 nM) to single bovine coronary venular endothelial cells (CVEC) while recording membrane potential (Em) or whole-cell current simultaneously with [Ca2+]i. The resting potential (Er) of unstimulated cells was bimodally distributed (-70 ± 9 mV, n = 26; -15 ± 8 mV, n = 30). Irrespective of Er, BK evoked a biphasic [Ca2+]i increase simultaneously with a change in Em. When Er was negative to -30 mV, depolarizations were typically observed. When Er was positive to -30 mV, transient hyperpolarizations were typically observed. Under voltage clamp, [Ca2+], increased as the membrane hyperpolarized and the ratio Δ[Ca2+]i/ΔEm was greater in the presence of BK than in unstimulated cells. Many, but not all, cells exhibited an outward K+ current that appeared to be Ca2+ dependent. When present, this current typically predominated over other cu...