(A) RT-PCR and genomic PCR amplification products of transfected MDCK-F cells, separated in an ethidium bromide-stained agarose gel. Loading: M, marker (506 and 1,018 bp). Lanes: 1–5, RT-PCR of MDCK-F cells; 1, nontransfected cells; 2, mock-transfected cells; 3, Kv1.4-transfected cells; 4, H2O control; 5, RT− control; 6–8, genomic PCR of MDCK-F cells; 6, nontransfected cells; 7, Kv1.4-transfected cells; 8, mock-transfected cells. (B) Southern blot hybridization with a digoxigenin-ddUTP-labeled Kv1.4-specific oligonucleotide. Only the stably transfected cell clones in lanes 3 and 7 exhibited the Kv1.4-specific, single 522-bp band in RT-PCR and genomic PCR experiments, as shown in A.