title: Ionic mechanisms involved in the secretory effects of histamine in the rat adrenal medulla.
abstract: Histamine activation of H1 receptors elicited the release of adrenaline from in vitro perfused rat adrenal with an EC50 of 3 microM. Neither Na+ deprivation nor complete membrane depolarization abolished the histamine-mediated secretory response but it was partially dependent on extracellular Ca2+. Nitrendipine and BAY-K-8644 affected the release induced by histamine concentrations at over 3 microM. Delayed application of histamine pulses, after external Ca2+ removal, led to a decline in to a plateau at 50% of the initial release. Pretreatment with ionomycin abolished this Ca2+ deprivation-resistant component. These data suggest that secretion evoked by low concentrations of histamine occurs by mobilization of Ca2+ from internal stores whereas higher concentrations use Ca2+ from both intracellular and extracellular sources.
authors.affiliation: Departamento de Farmacología y Medicina Física, Facultad de Medicina, Universidad de La Laguna, Tenerife, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Borges
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism*; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D009568:Nitrendipine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000502:physiology
chemical_list: D002395:Catecholamines; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D006632:Histamine; D009568:Nitrendipine; D012964:Sodium; D002118:Calcium