Kidney Function

TRPC5 forms non-selective cation channels. Here we studied the role of internal Ca2+ in the activation of murine TRPC5 heterologously expressed in human embryonic kidney cells. Cell dialysis with various Ca2+ concentrations (Ca2+i) revealed a dose-dependent activation of TRPC5 channels by internal Ca2+ with EC50 of 635.1 and 358.2 nm at negative and positive membrane potentials, respectively. Stepwise increases of Ca2+i induced by photolysis of caged Ca2+ showed that the Ca2+ activation of TRPC5 channels follows a rapid exponential time course with a time constant of 8.6 ± 0.2 ms at Ca2+i below 10 µm, suggesting that the action of internal Ca2+ is a primary mechanism in the activation of TRPC5 channels. A second slow activation phase with a time to peak of 1.4 ± 0.1 s w…