[The arrhythmogenicity of alpha 1-adrenergic stimulation following myocardial acidosis].
Ischemia is associated with myocardial acidosis which recovers upon reperfusion. In such conditions, alpha 1-adrenergic stimulation is arrhythmogenic. We used single cardiac myocytes loaded with the pH fluorescent dye, SNARF-1, to determine if a modulation of pH could explain the effect of alpha 1-adrenergic stimulation. Cells were exposed to acidosis (CO2 15%) for 15 min and then normocapnia restored. During acidosis, alpha 1-adrenergic stimulation caused an increase in pH which was abolished by blocking Na+/H+ exchange with ethylisopropylamiloride (EIPA). After removal of acidosis aftercontractions were manifest in 8 out of 10 and 1 out of 5 cells in the presence of an alpha 1-adrenergic agonist and in control, respectively (p < 0.001). EIPA abolished the occurrence of after contractions. Thus, the arrhythmogenicity of alpha 1-adrenergic stimulation depends on activation of Na+/H+ exchanger.
Gambassi
G
G
Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD.
Carbonin
P
P
Capogrossi
M C
MC
D000138:Acidosis / Q000150:complications* / Q000503:physiopathology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D001145:Arrhythmias, Cardiac / Q000209:etiology* / Q000503:physiopathology; D001578:Benzopyrans; D009202:Cardiomyopathies / Q000150:complications* / Q000503:physiopathology; D005453:Fluorescence; D005456:Fluorescent Dyes; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*
D000889:Anti-Arrhythmia Agents; D001578:Benzopyrans; D005456:Fluorescent Dyes; D011942:Receptors, Adrenergic, alpha; C063917:SNARF dye; D000584:Amiloride; C039614:ethylisopropylamiloride
Aritmogenicità della stimolazione alpha 1-adrenergica dopo acidosi miocardica.