Chloride and cation currents activated by bradykinin in coronary venular endothelial cells

Bradykinin (BK) is known to activate several types of ion channels in endothelial cells, including a K+ channel and a nonselective cation channel. The predominant BK-activated current in most endothelial cells appears to be an outward, Ca(2+)-activated K+ current. We consistently recorded a rapidly activated, spontaneously inactivated inward current stimulated by BK in bovine coronary venular endothelial cells (CVECs). With the use of a whole cell, perforated patch recording mode, the average magnitude of the current was -293 +/- 38 pA. Simultaneous measurements of current and intracellular Ca2+ concentration ([Ca2+]i) showed that the inward current correlated closely with transient increases in [Ca2+]i due to Ca2+ release from intracellular stores. The current could be blocked by 4,4'-diisothiocyanatostilbene-2, 2'-disulfonic acid (DIDS) but not by La3+, and it persisted in Ca(2+)-free/Na(+)-free solution. When intra- and/or extracellular Cl- concentrations were altered, the reversal potential of the current shifted according to the calculated Cl- -equilibrium potential, indicating that the current was carried primarily by Cl-. Another inward current was also activated by BK. This current was slower to activate, could be blocked by La3+, but was not blocked by DIDS. The time course of the slowly activated current correlated with the plateau phase of the BK-stimulated [Ca2+]i increase, which was similar to the behavior of a nonselective cation current reported previously. We propose that these two currents may contribute to the depolarizations and net inward currents induced by BK in this cell line.