Lack of Ca2+- and ATP-dependent priming stage in caffeine-induced exocytosis in bovine adrenal chromaffin cells: comparison with Ca2+.
1. Caffeine (20-40 mM) secreted catecholamines from beta-escin-permeabilized bovine adrenal chromaffin cells in the presence or absence of 2 mM MgATP. The caffeine-induced catecholamine secretion in the presence of MgATP was to the same extent as that in the absence of MgATP. 2. Ca2+ (0.1-10 microM) induced a significantly greater secretion of catecholamines in the presence of MgATP than in the absence of MgATP. 3. ML-9 (100 microM) and ML-7 (100 microM), myosin light chain kinase inhibitors, and W-7 (100 microM) and trifluoperazine (TFP; 30 microM), calmodulin antagonists, inhibited the Ca2+-induced catecholamine secretion in the presence of MgATP but not in the absence of MgATP. They did not inhibit the caffeine-induced catecholamine secretion in the presence of MgATP. 4. The ATP-independent phase in Ca2+-dependent exocytosis is thought to be associated with the final step that ultimately leads to fusion, while the ATP-dependent phase is thought to be associated with a vesicle priming reaction. Therefore, these results suggest that the ATP-requiring priming stage is lacking in the process of caffeine-induced exocytosis 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
H
H
Kimura
T
T
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000502:physiology*; D000311:Adrenal Glands / Q000187:drug effects; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002395:Catecholamines / Q000378:metabolism; D002478:Cells, Cultured; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D019439:Chromaffin Cells / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors
D002147:Calmodulin; D002395:Catecholamines; D000697:Central Nervous System Stimulants; D004791:Enzyme Inhibitors; D002110:Caffeine; D000255:Adenosine Triphosphate; D009219:Myosin-Light-Chain Kinase; D002118:Calcium