Myosin light chain kinase inhibitors and calmodulin antagonist inhibit Ca(2+)- and ATP-dependent catecholamine secretion from bovine adrenal chromaffin cells.
We have used stage-specific assays for ATP-dependent priming and for Ca(2+)-activated triggering in the absence of ATP to examine the effects of myosin light chain kinase (MLCK) inhibitors, ML-9 and ML-7, and calmodulin antagonists, W-7 and trifluoperazine (TFP), on regulated exocytosis in beta-escin-permeabilized bovine adrenal chromaffin cells. Ca2+ (0.1-30 microM) induced a significantly greater secretion of catecholamines in the presence of MgATP (2 mM) than in the absence of MgATP. ML-9 (30 and 100 microM), ML-7 (30 and 100 microM), W-7 (30 and 100 microM) and TFP (10 and 30 microM) inhibited the Ca(2+)-induced catecholamine secretion in the presence of MgATP, but did not affect the catecholamine response to Ca2+ in the absence of MgATP. In intact cells all these compounds inhibited catecholamine secretion in responses to acetylcholine (100 microM) and high K+ (40 mM). The results obtained in permeabilized cells suggest that the calmodulin-MLCK system plays an essential role in the ATP-requiring priming stage but not in the Ca2(+)-triggered fusion step in the exocytotic process in bovine adrenal chromaffin cells.
Matsumura
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C
Department of Dental Pharmacology, The Nippon Dental University School of Dentistry at Niigata, Hamauracho, Japan.
Kuwashima
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Kimura
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T
D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000311:Adrenal Glands / Q000378:metabolism; D000818:Animals; D001381:Azepines; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004928:Escin / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects*; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors*; D009281:Naphthalenes; D011188:Potassium / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology
D001381:Azepines; D002147:Calmodulin; D002395:Catecholamines; D004791:Enzyme Inhibitors; D009281:Naphthalenes; C056218:ML 9; C070571:ML 7; D014268:Trifluoperazine; D004928:Escin; D000255:Adenosine Triphosphate; D009219:Myosin-Light-Chain Kinase; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium