The effects of extracellular potassium and several drugs on the premature action potential and postextrasystolic potentiation.
| Title: | The effects of extracellular potassium and several drugs on the premature action potential and postextrasystolic potentiation. |
|---|---|
| Authors: | Linuma H; Kato K |
| Source: | European journal of cardiology [Eur J Cardiol] 1978 Jul; Vol. 7 (5-6), pp. 465-77. |
| Publication Type: | Journal Article |
| Language: | English |
| Journal Info: | Publisher: Excerpta Medica Country of Publication: Netherlands NLM ID: 0404054 Publication Model: Print Cited Medium: Print ISSN: 0301-4711 (Print) Linking ISSN: 03014711 NLM ISO Abbreviation: Eur J Cardiol Subsets: MEDLINE |
| Imprint Name(s): | Publication: Amsterdam : Excerpta Medica; Original Publication: Amsterdam [Elsevier/North-Holland Biomedical Press, etc.] |
| MeSH Terms: | Caffeine/*pharmacology ; Cardiac Complexes, Premature/*physiopathology ; Extracellular Space/*drug effects ; Myocardial Contraction/*drug effects ; Potassium/*pharmacology ; Verapamil/*pharmacology; Action Potentials/drug effects ; Calcium/metabolism ; Heart Conduction System/drug effects ; Heart Conduction System/physiopathology ; Isoproterenol/pharmacology ; Myocardium/metabolism ; Animals ; Dogs |
| Abstract: | To investigate the mechanism of postextrasystolic potentiation of contraction (PESP), the effects of extracellular K concentration, isoproterenol, verapamil and caffeine were examined in canine ventricular muscle. The muscles were driven at 1 Hz, then a premature stimulus was applied to elicit a premature action potential and after a compensatory pause postextrasystolic stimulus was applied to induce PESP. At 5.9 mM K the premature action potential had a longer plateau than the preceding control action potential. The prolongation was dependent on the proximity, i.e. the interval between the premature stimulus and the preceding control action potential; the maximal enhancement of about 25% was obtained with a proximity of 70 ms. In parallel with this prolongation the post-extrasystolic contraction was increased more than 5-fold. However, PESP was obtained without prolongation of the premature action potential when [K]0 was reduced to 1.2 mM. Similarly, PESP under the effect of 10(-6) g/ml isoproterenol or 10(-5) M verapamil was not accompanied by prolongation of the premature action potential. Thus it is difficult to explain the PESP solely by the increased Ca influx during the premature action potential. Since caffeine abolished PESP, some other effects of the premature beat on sarcoplasmic reticulum might be responsible for the PESP. |
| Substance Nomenclature: | 3G6A5W338E (Caffeine); CJ0O37KU29 (Verapamil); L628TT009W (Isoproterenol); RWP5GA015D (Potassium); SY7Q814VUP (Calcium) |
| Entry Date(s): | Date Created: 19780701 Date Completed: 19781220 Latest Revision: 20131121 |
| Update Code: | 20260130 |
| PMID: | 81131 |
| Database: | MEDLINE |
Journal Article