Expression of L-type (α1D subunit) and T-type (α1G and α1H subunit) Ca2+ channels in epithelial-derived human breast cancer cells (ZR-75-1)

Using the video imaging technique this group has previously reported that regulatory volume decrease (RVD) in ZR-75-1 cells is Ca2+ dependent. RVD was inhibited in the absence of external Ca2+ and in the presence of voltage-gated Ca2+ channel inhibitors, nifedipine (L-type) and flunarizine (T-type; Ashes et al. 2002). These results suggested that external Ca2+ entered the cell via voltage-gated L- and/or T-type Ca2+ channels. In this study, the expression of L- and T-type channels was investigated in ZR-75-1 cells using reverse transcriptase-polymerase chain reaction (RT-PCR). The α1C and α1D are subunits of the L-type Ca2+ channel. The α1C subunit is expressed in cardiac muscle and the α1D subunit in the CNS and endocrine cells, where it may have a role in stimulus-secretion coupling. The α1G, α1H and α1I subunits have been cloned and display biophysical and pharmacological properties of native T-type Ca2+ channels when overexpressed in Xenopus oocytes or HEK-293 cells (Randall & Benham 1999).