Bradykinin-induced increases in cytosolic calcium and ionic currents in cultured bovine aortic endothelial cells.

Abstract

The goal of the present study was to determine if voltage-sensitive calcium channels are present in bovine aortic endothelial cell plasmalemma and if they contribute to the rise in cytosolic calcium produced by bradykinin. After bradykinin (100 nM) exposure, endothelial cell associated fura-2 fluorescence peaked within 10-20 seconds and then declined to a steady level 2- to 3-fold above resting values. Pretreatment with lanthanum (20 microM) abolished the steady level produced by bradykinin but had little effect on the initial, transient rise in cytosolic calcium. Chelation of extracellular calcium with EGTA before addition of bradykinin resulted in a substantial decrease in the fura-2 transient and elimination of the long-lasting component. Nimodipine (3 microM) and nitrendipine (1 microM) were without effect on either phase of the bradykinin-induced response. Moreover, elevation of extracellular potassium failed to produce a rise in intracellular calcium. With the use of the tight seal technique to voltage clamp the cells, inwardly rectifying and calcium-activated potassium currents were found to exist in the endothelial cells. Addition of bradykinin (100 nM) elicited a calcium-activated potassium current that was eliminated in the absence of intracellular potassium. No voltage-sensitive calcium currents were activated when the cells were exposed to 10 mM or 110 mM calcium chloride in the presence or absence of bradykinin. The binding of [3H](+)PN200-110 to endothelial cell membrane preparations was 1-3 orders of magnitude lower than that observed in PC-12, GH3, or BC3H1 cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)