Bradykinin-evoked modulation of cytosolic Ca2+ concentrations in cultured renal epithelial (MDCK) cells

We have investigated the effect of bradykinin on cytosolic Ca2+ concentrations of renal MDCK cells cultured as monolayers. Bradykinin rapidly (within 5 to 20 s) increased cytosolic Ca2+ concentrations, measured by using the fluorescent indicator quin-2, from the basal value of 103 nM to a maximal value of 578 nM at about 10(-8) M bradykinin. The increase of Ca2+ was transient, returning to baseline within 1.5 to 2 min. The transient response appeared to be due to cell desensitization rather than peptide degradation. Previously desensitized cells could be resensitized after a 10 min incubation in the absence of bradykinin. The removal of extracellular Ca2+ or the addition of verapamil did not have a major effect on the maximal bradykinin-evoked changes of Ca2+, suggesting that Ca2+ released from intracellular stores plays a pivotal role in this process. Bradykinin-evoked Ca2+ metabolism may play an important role as modulator of the cellular functions of MDCK cells.