The effect of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) on muscarinic receptor-induced Ca2+ mobilization in a human salivary epithelial cell line.
We have investigated the effect of W-7, a calmodulin (CaM) antagonist, on Ca2+ mobilization in a human salivary epithelial cell line, HSG-PA, after muscarinic receptor stimulation. In a medium containing 1.5 mmol/l Ca2+, W-7 reduced both the maximum peak increase in cytosolic Ca2+ [( Ca2+]i) which follows stimulation by carbachol (Cch, 100 mumol/l) and the sustained nature of the response. Using an experimental approach which allows separate visualization of the intracellular Ca2+ release and extracellular Ca2+ entry phases, W-7 was shown preferentially to inhibit Ca2+ release. At 100 mumol/l W-7, Cch-induced Ca2+ release was completely inhibited, but Cch-induced Ca2+ entry was partially (approximately 40%) maintained. This W-7 residual Ca2+ entry response was abolished when cells were depolarized with high K+ or gramicidin D. W-7 also substantially inhibited Cch-induced inositol trisphosphate (IP3) production (approximately 5%). W-5, a less potent CaM antagonist than W-7, had markedly smaller effects on Cch-induced Ca2+ mobilization and IP3 formation. W-7 (100 mumol/l) completely blocked (comparable to 10 mumol/l atropine) the binding of the muscarinic antagonist [3H] quinuclidinyl benzilate (QNB) to muscarinic receptors on cell membranes, whereas Cch (at 100 mumol/l) had minimal effects on ligand binding. W-7 and W-5 were equipotent in their ability to inhibit [3H] QNB binding. These results suggest that W-7 reduces Ca2+ mobilization in HSG-PA cells by a mechanism which likely involves the antagonism of a CaM regulatory step(s) but may also involve at least a partial blockade of the muscarinic receptor.
He
X J
XJ
Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, MD 20892.
Wu
X Z
XZ
Baum
B J
BJ
D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D011813:Quinuclidinyl Benzilate / Q000378:metabolism / Q000494:pharmacology; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D012469:Salivary Glands / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology*
D002147:Calmodulin; D011976:Receptors, Muscarinic; D013449:Sulfonamides; C017967:W 7; D011813:Quinuclidinyl Benzilate; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D002118:Calcium