Methods for Studying Voltage-Gated Sodium Channels in Heterologous Expression Systems

The discovery that oocytes of the frog Xenopus laevis can be induced to express working membrane ion channels by introducing channel mRNA into their cytoplasm (heterologous expression) has greatly impacted the field of ion channel physiology. With the addition of site-directed mutagenesis techniques, the functional consequences of virtually any mutation can now be specifically and easily assessed. Here, we describe an effective procedure for investigating cardiac sodium channel gating (hNa_V 1.5) both in Xenopus oocytes, and in a mammalian expression system, human embryonic kidney (HEK) 293 cells. We describe cell attached patch clamp for oocytes, and whole cell voltage clamp in HEK 293 cells.