title: Dogfish pressor response to potassium blocked by magnesium and phentolamine.
abstract: In vivo infusion of MgCl2 blocks the dogfish pressor response to K+. This action of Mg2+ was contrasted to phentolamine in in vivo and in vitro experiments. Mg2+ blocks the spontaneous release of catecholamines from dogfish chromaffin tissue but does not alter the norepinephrine-induced contraction of the isolated dogfish artery. In vivo infusion of Mg2+ causes a significant decrease in resting catecholamine levels and diminishes the catecholamine release caused by K+ challenge. Both Mg2+ and phentolamine block the pressor action of K+, Mg2+ by preventing the K+-induced release of catecholamines and phentolamine by preventing the circulating catecholamines from interacting with alpha-adrenergic receptor sites.
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002395:Catecholamines / Q000494:pharmacology; D002838:Chromaffin System / Q000502:physiology*; D004284:Dogfish / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D012754:Sharks / Q000502:physiology*
chemical_list: D002395:Catecholamines; D008274:Magnesium; D011188:Potassium; D010646:Phentolamine