BRADYKININ-ACTIVATED CALCIUM INFLUX PATHWAY IN BOVINE AORTIC ENDOTHELIAL-CELLS

Clusters of electrically coupled endothelial cells were used to characterize a bradykinin (BK)-activated Ca2+ influx pathway. Spatial voltage control of clusters containing three to eight cells, evaluated as the ratio of the voltage response in one cell to a voltage pulse in the most distant cell of the cluster, was 0.96 at a holding potential of 0 mV in normal saline bath and 0.88 in the presence of BK. BK activated an inward current that was carried by either Na+ or Ca2+ when the membrane potential was held at -60 mV. Current was activated within 3 s of application of BK and peaked within 1 min. With Ca2+ as the permeable extracellular ion the current was stable for 1-3 min and then declined over a period of 5-8 min in the continued presence of BK. However, when Na+ carried the current it was sustained over a 10-min test period. The reversal potential of the BK-activated current was near 0 mV, suggesting activation of a nonspecific cation channel(s). The inward current at -60 mV averaged 13 +/- 4.5 pA (n = 9)/cell in Ca2+ and 12.2 +/- 9.3 pA (n = 5)/cell in Na+. Both Na+ and Ca2+ currents were blocked by 200-mu-M lanthanum.