Bradykinin-induced potassium current in cultured bovine aortic endothelial cells

Abstract

Bovine aortic endothelial cells (BAECs) respond to bradykinin with an increase in cytosolic-free Ca2+ concentration, [Ca2+]i, accompanied by an increase in surface membrane K+ permeability. In this study, electrophysiological measurement of K+ current was combined with 86Rb+ efflux measurements to characterize the K+ flux pathway in BAECs. Bradykinin- and Ca2(+)-activated K+ currents were identified and shown to be blocked by the alkylammonium compound, tetrabutylammonium chloride and by the scorpion toxin, noxiustoxin, but not by apamin or tetraethylammonium chloride. Whole-cell and single-channel current analysis suggest that the threshold for Ca2+ activation is in the range of 10 to 100 nM [Ca2+]i. The whole-cell current measurements show voltage sensitivity only at the membrane potentials more positive than 0 mV where significant current decay occurs during a sustained depolarizing pulse. Another K+ current present in control conditions, an inwardly rectifying K+ current, was blocked by Ba2+ and was not affected by noxiustoxin or tetrabutylammonium chloride. Efflux of 86Rb+ from BAEC monolayers was stimulated by both bradykinin and ionomycin. Stimulated efflux was blocked by tetrabutyl- and tetrapentyl-ammonium chloride and by noxiustoxin, but not by apamin or furosemide. Thus, 86Rb+ efflux stimulated by bradykinin and ionomycin has the same pharmacological sensitivity as the bradykinin- and Ca2(+)-activated membrane currents. The results confirm that bradykinin-stimulated 86Rb+ efflux occurs via Ca2(+)-activated K+ channels. The blocking agents identified may provide a means for interpreting the role of the Ca2(+)-activated K+ current in the response of BAECs to bradykinin.

Effects of vasoactive agonists on the membrane potential of cultured bovine aortic and guinea‐pig coronary endothelium.

“…This result is consistent with our previous findings in GCECs (Mehrke & Daut, 1990) suggesting that the agonist-induced changes in the membrane potential of endothelial cells are mainly due to changes in sub-membrane intracellular calcium and the subsequent increase in the open probability of Ca2+-activated K+ channels. Single-channel recordings suggest that the 'threshold' for Ca2+ activation of these channels may be below 400 nm (Sauve et al 1988), possibly even below 100 nm (Colden-Stanfield et al 1990). …”

“…This hyperpolarization may be due to an increased open probability of Ca2+-activated K+ channels caused by a rise in [Ca2+]i (Sauve, Parent, Simoneau & Roy, 1988;Colden-Stanfield, Schilling, Possani & Kunze, 1990). On the other hand, the rise in [Ca2+]i induced by bradykinin or ATP was found to be increased by hyperpolarization of the endothelium (Schilling, 1989;Laskey, Adams, Johns, Rubanyi & van Breemen, 1990;Liickhoff & Busse, 1990).…”

Nitric oxide – the endothelium-derived relaxing factor and its role in endothelial functions

“…In endothelial cells, the production or release of NO is preceded or accompanied by enhanced phosphatidyl inositol (PI) turnover and increase in concentration of the resting free cytosolic calcium ([Ca 2+ ] i ) (Büsse et al 1988;Stanfield et al 1990;Vanhoutte and Eber 1991;Adams et al 1993 (Johns et al 1987;Ryan 1989;Elliot et al 1992). An increase of free [Ca 2+ ] i is a signal for increased production of NO by endothelium (Wong and Klassen 1992).…”

Regulation of L‐arginine transport and nitric oxide release in superfused porcine aortic endothelial cells.

“…We then investigated whether the transient stimulation of L-arginine transport and synthesis of NO and PGI2, induced by bradykinin , was related to altered membrane potential. Agonists such as bradykinin or ATP, or changes in flow, hyperpolarize the endothelial plasma membrane and enhance NO production (Busse, Fichtner, Liickhoff & Kohlhardt, 1988;Nakache & Gaub, 1988; Schilling, 1989; Colden-Stanfield, Schilling (Schilling, 1989;Busse et al 1989;Colden-Stanfield et al 1990), which increases the driving force for L-arginine entry into the endothelial cell via system y+ (Bussolati et al 1993;Kavanaugh, 1993). Entry of L-arginine is inhibited by other cationic arginine analogues, including the eNOS inhibitors L-NMMA and L-NIO.…”