Paradoxical facilitation of exocytosis by inhibition of L-type calcium channels of bovine chromaffin cells |
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| Authors: | Rosa Juliana M Conde Marina Nanclares Carmen Orozco Angela Colmena Inés de Pascual Ricardo García Antonio G Gandía Luis |
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| Institution: | aInstituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain;bDepartamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain;cInstituto de Investigación Sanitaria, Servicio de Farmacología Clínica, Hospital Universitario de la Princesa, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain |
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| Abstract: | Ca2+ entry through the L-subtype (α1D, Cav1,3) of voltage-dependent calcium channels (VDCCs) seems to selectively regulate the endocytotic response after the application of a single depolarizing pulse to voltage-clamped bovine chromaffin cells. Here we have found that L channel blockade with nifedipine transformed the exocytotic responses elicited by a double-pulse protocol, from depression to facilitation. This apparent paradoxical effect was mimicked by pharmacological interventions that directly block endocytosis namely, dynasore, calmidazolium, GTP-γS and GDP-βS. This reinforces our view that Ca2+ entry through PQ channels (α1A; Cav2.1) regulates fast exocytosis while Ca2+ entry through L channels preferentially controls rapid endocytosis. |
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| Keywords: | Endocytosis Exocytosis Double-pulse Facilitation Chromaffin cells Calcium channels |
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