mast-cell-degranulating-peptide and Prostatic-Neoplasms

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 patchclamp 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 microM 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 microM. The K+ channel open probability was inhibited by alpha-dendrotoxin (DTX) (with a half-blocking concentration of approximately 5 nM) and mast cell degranulating peptide (MCDP) (with half-blocking concentration of approximately 70 nM) at 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.

Topics: Adenocarcinoma; Calcium; Charybdotoxin; Elapid Venoms; Humans; Ion Channel Gating; Ion Transport; Lymphatic Metastasis; Male; Neoplasm Proteins; Neoplasms, Hormone-Dependent; Patch-Clamp Techniques; Peptides; Potassium Channel Blockers; Prostatic Neoplasms; Quinidine; Tetraethylammonium; Tumor Cells, Cultured

Very little is known about the expression of ion channels in prostate cells (both normal and malignant), and their possible role in physiological and pathological functions. We therefore studied ion conductances and their role in the proliferation of LNCaP cells, an androgen-sensitive human prostate cancer cell line.. We applied patch-clamp recording techniques for electrophysiological studies, and 3H-thymidine incorporation and protein content assays for cell growth studies.. Only one type of voltage-dependent ion conductance, a potassium K+ conductance, was identified. This current, which was depressed by a rise in intracellular Ca2+, had a high sensitivity to tetraethylammonium (TEA) (with half-block at 2 mM) and was also inhibited by 2 nM alpha-dendrotoxin (DTX) and 20 nM mast-cell degranulating peptide (MCDP). K+ channel inhibitors inhibited [3H]thymidine incorporation and protein content, in a dose-dependent fashion, indicating that K+ channels are involved in cell growth.. We conclude from our findings that the human cancer prostate cell line LNCaP has a new type of K+ channel, likely to play an essential role in the physiology of these cells and, more specifically, in cell proliferation.

Topics: Androgens; Apoptosis; Calcium; Cell Division; Elapid Venoms; Humans; Male; Membrane Potentials; Patch-Clamp Techniques; Peptides; Potassium; Potassium Channels; Prostatic Neoplasms; Tetraethylammonium; Thymidine; Tritium; Tumor Cells, Cultured