Kt. Izutsu et al., CHARACTERISTICS AND REGULATION OF A MUSCARINICALLY ACTIVATED K-CURRENT IN HSG-PA CELLS, The American journal of physiology, 266(1), 1994, pp. 30000058-30000066
Whole cell currents were measured in HSG-PA cells (a proposed model fo
r salivary gland duct cells) after muscarinic receptor activation or e
xposure to known signaling agents. Exposure to carbachol or oxotremori
ne M produced large and often oscillatory increases in outward current
whose reversal potentials indicated a K current. The current was sens
itive to extracellular atropine, charybdotoxin, and quinine, but not a
pamin, and to ,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
in the pipette. The response was prolonged or increased by guanosine 5
'-O-(3-thiotriphosphate) and mimicked by D-myo-inositol 1,4,5-trisphos
phate (IP3) or heparin in the pipette and by extracellular Ca ionophor
es. Tetraethylammonium indirectly inhibited the response via the musca
rinic receptor. Fura 2 in cell suspensions showed that muscarinic agon
ists increased cytosolic Ca ion concentration ([Ca2+](i)) five to seve
nfold, and measurements with indo 1 in individual cells showed that th
e oscillatory changes in outward current were tightly correlated with
parallel changes in [Ca2+](i). The results indicate that muscarinic re
ceptor stimulation of HSG-PA cells activates Ca2+-activated K channels
through a signaling pathway involving a G protein, IP3 production, an
d increased [Ca2+](i) levels. These findings are similar to those in s
alivary gland acinar cells.