Characterization of Ca2+-inhibited potassium channels in the LNCaP human prostate cancer cell line

Potassium plasma membrane channels have been studied in the LNCaP androgen-sensitive human prostate cancer cell line, derived from a lymph node of a subject with metastatic carcinoma of the prostate, Membrane currents were recorded by the patch clamp technique, using the cell-attached, cell-free and whole-cell mode. A voltage-dependent, non-inactivating potassium channel (delayed rectifier) was the most commonly observed ion channel in LNCaP cells. The slope conductance of K+ channels in a symmetrical 140 mM K+ gradient was 78 pS, In excised inside-out patches, the channel was inhibited by increasing the cytoplasmic Ca2+ concentration (with half-block at 0.5 mu M Ca2+) over a wide range of membrane potentials. The K+ channel had a high sensitivity to tetraethylammonium (TEA), that reduced the single channel conductance with Kd of 280 +/- 27 mu M. The K+ channel open probability was inhibited by a dendrotoxin (DTX) (with a half-blocking concentration of similar to 5 nM) and mast cell degranulating peptide (MCDP) (with half-blocking concentration of similar to 70 nM) ac all membrane potentials and with very slow reversibility, In view of the biophysical and pharmacological properties of K+ channels in LNCaP cells, it is not possible to classify these channels as one of the previously characterized types of voltage- or ligand-gated K+ channels in other cell lines.