title: 4-Aminopyridine can induce release of calcium from the sarcoplasmic reticulum of frog heart.
abstract: 4-Aminopyridine (4-AP), a K(+)-channel blocker, has been associated with cellular Ca2+ movements in various excitable tissues but its interaction with intracellular Ca2+ pools has not been described. Spontaneously beating ventricular strips of frog hearts responded to 4-AP (1.6 x 10(-2) M) by contracture that was susceptible to tolerance development when 4-AP was applied in a repetitive manner after washout periods. Under full mechanical inhibition by Ca(2+)-free Ringer or high-K+ Ringer or a combination of both, 4-AP could still produce contracture, a finding indicating that the source of Ca2+ for such an effect should be intracellular Ca2+ pools, namely the sarcoplasmic reticulum. It was concluded that 4-AP could induce release of Ca2+ from internal stores that might be of importance in its cardiac actions.
authors.affiliation: Department of Pharmacology, Cerrahpapa Faculty of Medicine, University of Istanbul, Turkey.
authors.forename: M
authors.initials: M
authors.lastname: Ozgül
authors.forename: C
authors.initials: C
authors.lastname: Silan
authors.forename: O
authors.initials: O
authors.lastname: Yillar
authors.forename: C
authors.initials: C
authors.lastname: Küçükhüseyin
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003655:Decerebrate State / Q000503:physiopathology; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D026902:Potassium Channel Blockers; D011895:Rana ridibunda; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*
chemical_list: D026902:Potassium Channel Blockers; D015761:4-Aminopyridine; D002118:Calcium