title: A calcium ionophore simulating the action of epinephrine on the alpha-adrenergic receptor.
abstract: Calcium acting through the ionophore A-23187 caused massive K(+) release from rat parotid slices. The ionophore thus simulates the action of epinephrine on the alpha-adrenergic receptor in this system. The alpha-adrenergic and cholinergic receptors are, however, not involved in the action of the ionophore since phetolamine and atropine had no effect on the ionophore-induced K(+) release. Amylase secretion, which is induced by epinephrine through the beta-adrenergic receptor but does not require Ca(++) in the medium, was only slightly increased by the ionophore in the presence of Ca(++). The K(+) released by Ca(++) through the ionophore was regained by the cells upon chelation of Ca(++) with ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid. Similar to the action of epinephrine on the alpha-adrenergic receptor, the K(+) release induced by the ionophore is specific for Ca(++), which cannot be substituted by 2.5 mM Sr(++), Mg(++), or Ba(++). The results suggest that epinephrine, like the ionophore, introduces Ca(++) into the cell to mediate K(+) release. It is proposed that the ionophore A-23187 may be an effective probe to test whether other Ca(++)-requiring hormones and neurotransmitters act in a similar fashion to produce their diverse physiological responses.
mesh_terms: D000085:Acetates / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000681:Amylases / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002132:Calcium Radioisotopes; D002264:Carboxylic Acids / Q000494:pharmacology; D002614:Chelating Agents / Q000494:pharmacology; D046508:Culture Techniques; D004837:Epinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006018:Glycols / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats
chemical_list: D000085:Acetates; D000316:Adrenergic alpha-Agonists; D000900:Anti-Bacterial Agents; D002132:Calcium Radioisotopes; D002264:Carboxylic Acids; D002614:Chelating Agents; D006018:Glycols; D001285:Atropine; D000681:Amylases; D008274:Magnesium; D011188:Potassium; D002118:Calcium; D004837:Epinephrine; D010646:Phentolamine