title: Hypoxia-elicited catecholamine release is controlled by L-type as well as N/PQ types of calcium channels in rat embryo chromaffin cells.
abstract: At early life, the adrenal chromaffin cells respond with a catecholamine surge under hypoxic conditions. This response depends on Ca(2+) entry through voltage-activated calcium channels (VACCs). We have investigated here three unresolved questions that concern this response in rat embryo chromaffin cells (ECCs): 1) the relative contribution of L (α1D, Cav1.3), N (α1B, Cav2.2), and PQ (α1A, Cav2.1) to the whole cell Ca(2+) current (ICa); 2) the relative contribution of L and N/PQ channels to the cytosolic Ca(2+) elevations triggered by hypoxia (Δ[Ca(2+)]c); and 3) the role of L and non-L high-VACCs in the regulation of the catecholamine surge occurring during prolonged (1 min) hypoxia exposure of ECCs. Nimodipine halved peak ICa and blocked 60% the total Ca(2+) entry during a 50-ms depolarizing pulse to 0 mV (QCa). Combined ω-agatoxin IVA plus ω-conotoxin GVIA (Aga/GVIA) blocked 30% of both ICa peak and QCa. This relative proportion of L- and non-L VACCs was corroborated by Western blot that indicated 55, 23, and 25% relative expression of L, N, and PQ VACCs. Exposure of ECCs to hypoxia elicited a mild but sustained Δ[Ca(2+)]c; the area of Δ[Ca(2+)]c was blocked 50% by nifedipine and 10% by Aga/GVIA. Exposure of ECCs to 1-min hypoxia elicited an initial transient burst of amperometric secretory spikes followed by scattered spikes along the time of cell exposure to hypoxia. This bulk response was blocked 85% by nimodipine and 35% by Aga/GVIA. Histograms on secretory spike frequency vs. time indicated a faster initial inactivation when Ca(2+) entry took place through N/PQ channels; more sustained secretion but at a lower rate was associated to Ca(2+) entry through L channels. The results suggest that the HIS response may initially be controlled by L and P/Q channels, but later on, N/PQ channels inactivate and the delayed HIS response is maintained at lower rate by slow-inactivating L channels.
authors.affiliation: Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain;
authors.forename: José-Carlos
authors.initials: JC
authors.lastname: Fernández-Morales
authors.affiliation: Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain;
authors.forename: Juan-Fernando
authors.initials: JF
authors.lastname: Padín
authors.affiliation: Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain;
authors.forename: Juan-Alberto
authors.initials: JA
authors.lastname: Arranz-Tagarro
authors.affiliation: Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Vestring
authors.affiliation: Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; Servicio de Farmacología Clínica, Instituto de Investigación Sanitaria, Hospital Universitario de la Princesa, Universidad Autónoma de Madrid, Madrid, Spain; and agg@uam.es antoniomiguel.garcia@uam.es.
authors.forename: Antonio G
authors.initials: AG
authors.lastname: García
authors.affiliation: Instituto Teófilo Hernando, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain; agg@uam.es antoniomiguel.garcia@uam.es.
authors.forename: Antonio Miguel G
authors.initials: AM
authors.lastname: de Diego
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000502:physiology; D020746:Calcium Channels, L-Type / Q000378:metabolism / Q000502:physiology*; D020864:Calcium Channels, N-Type / Q000378:metabolism / Q000502:physiology*; D020865:Calcium Channels, P-Type / Q000378:metabolism / Q000502:physiology*; D020907:Calcium Channels, Q-Type / Q000378:metabolism / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000378:metabolism* / Q000502:physiology; D004622:Embryo, Mammalian / Q000378:metabolism / Q000502:physiology; D051381:Rats
chemical_list: D020746:Calcium Channels, L-Type; D020864:Calcium Channels, N-Type; D020865:Calcium Channels, P-Type; D020907:Calcium Channels, Q-Type; D002395:Catecholamines
keywords: hypoxia; rat embryo chromaffin cells; voltage-activated calcium channels