Peak current densities and persistent currents.

For measurements of persistent Na+ currents, we used the Xenopus oocyte system and undiluted cRNA preparations (∼1–2 µg/µl) for injection in order to increase this small current fraction. This resulted in transient Na+ currents >10 µA in 96 mM external Na+. In none of the channels investigated, a significant increase of the persistent current fraction could be observed. Low expression levels of hNav1.5d and T1620Kd did not allow for an accurate determination of the persistent current fraction. As a positive control, we used cRNA for ΔKPQ channels, the first known LQT3 mutant. Respective values for Ipersistent/Itransient were: 179±42×10−3 at −30 mV, and 159±27×10−3 at −10 mV (n = 7).*Indicates pv1.5 splice variant versus hNav1.5.§Indicates p#Indicates pv1.5 variant.