N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (w7) stimulation of K + transport in a human salivary epithelial cell line

Abstract

Treatment of a human salivary epithelial cell line, HSG-PA, with the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7; 20–70 μM) increased 86Rb (K +) influx and efflux in a manner similar to that resulting from muscarinic (carbachol; Cch) or calcium ionophore (A23187) stimulation. Unlike the Cch or A23187 responses, the W7 responses were not blocked by 0.1 mM atropine (muscarinic antagonist) or phorbol-12-myristate-13-acetate (0.1 μM). Like Cch- or A23187-stimulated 86Rb fluxes, W7-stimulated 86Rb fluxes were substantially blocked by the K + channel inhibitors quinine (0.25 mM) and scorpion venom-containing charybdotoxin (33 μg/mL), while 5 mM tetraethylammonium chloride (K + channel blocker), furosemide (0.1 mM; Na +, K +, 2Cl − co-transport inhibitor) and ouabain (10 μM; Na +, K +-ATPase inhibitor) were ineffective. Purified charybdotoxin (10 nM) also blocked W7-stimulated 86Rb influx, as well as 86Rb influx stimulated by Cch or A23187. Although Quin 2 fluorescence measurements indicated that W7 increased free intracellular Ca 2+ concentration ([Ca 2+] i), the magnitude of the increase appeared to be insufficient to solely account for the W7-stimulated increases in 86Rb fluxes (i.e. K + channel activity). Ca 2+ was involved in the W7 response, however, as lack of Ca 2+ in the incubation medium reduced the W7-stimulated increases in 86Rb influx and efflux. Taken together, our results suggest that W7 increased K + fluxes in HSG-PA cells by interacting, directly or indirectly, with the K + transport machinery (K + channels) in a manner different from that observed during muscarinic stimulation, and also in a manner not accounted for solely by the formation of a typical muscarinic- or calcium ionophore-generated calcium signal.