title: Q- and L-type Ca2+ channels dominate the control of secretion in bovine chromaffin cells.
abstract: Potassium-stimulated catecholamine release from superfused bovine adrenal chromaffin cells (70 mM K+ in the presence of 2 mM Ca2+ for 10 s, applied at 5-min intervals) was inhibited by the dihydropyridine furnidipine (3 microM) by 50%. omega-Conotoxin MVIIC (CTx-MVIIC, 3 microM) also reduced the secretory response by about half. Combined CTx-MVIIC plus furnidipine blocked 100% catecholamine release. 45Ca2+ uptake and cytosolic Ca2+ concentrations ([Ca2+]i) in K(+)-depolarized cells were partially blocked by furnidipine or CTx-MVIIC, and completely inhibited by both agents. The whole cell current through Ca2+ channels carried by Ba2+ (IBa) was partially blocked by CTx-MVIIC. Although omega-conotoxin GVIA (CTx-GVIA, 1 microM) and omega-agatoxin IVA (Aga-IVA, 0.2 microM) partially inhibited 45Ca2+ entry, IBa and the increase in [Ca2+]i, the combination of both toxins did not affect the K(+)-evoked secretory response. The results are compatible with the presence in bovine chromaffin cells of a Q-like Ca2+ channel which has a prominent role in controlling exocytosis. They also suggest that Q- and L-type Ca2+ channels, but not N- or P-types are localized near exocytotic active sites in the plasmalemma.
authors.affiliation: Departamento de Farmacología, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
authors.forename: M G
authors.initials: MG
authors.lastname: López
authors.forename: M
authors.initials: M
authors.lastname: Villarroya
authors.forename: B
authors.initials: B
authors.lastname: Lara
authors.forename: R
authors.initials: R
authors.lastname: Martínez Sierra
authors.forename: A
authors.initials: A
authors.lastname: Albillos
authors.forename: A G
authors.initials: AG
authors.lastname: García
authors.forename: L
authors.initials: L
authors.lastname: Gandía
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001464:Barium / Q000378:metabolism; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000145:classification / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D004553:Electric Conductivity; D008954:Models, Biological; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002395:Catecholamines; D009467:Neuromuscular Depolarizing Agents; D001464:Barium; D011188:Potassium; D002118:Calcium