[The effect of alpha 1-adrenergic stimulation of the myocardium depends on the opposite actions of 2 receptor subtypes].
Two different myocardial alpha 1-adrenergic receptor subtypes have been recently described. Since their functional role is still unknown we examined the effect of alpha 1A and alpha 1B on contractile properties, cell Ca2+ homeostasis and myofilament sensitivity to Ca2+ in indo-1 loaded ventricular myocytes. Non selective alpha 1-adrenergic stimulation increases twitch amplitude, systolic Ca2+ and myofilament sensitivity. Same effects but amplified are associated with alpha 1A-receptors stimulation. In contrast, alpha 1B-receptors stimulation decreases twitch amplitude and systolic Ca2+ below control value. Myocardial alpha 1-adrenergic stimulation results from the opposite actions of the 2 subtypes.
Gambassi
G
G
Laboratory of Cardiovascular Science, National Institute on Aging, National Institutes of Health, Baltimore, MD.
Capogrossi
M C
MC
D000818:Animals; D002118:Calcium / Q000502:physiology; D004558:Electric Stimulation; D005453:Fluorescence; D005456:Fluorescent Dyes; D006321:Heart / Q000502:physiology*; D066298:In Vitro Techniques; D007211:Indoles; D009200:Myocardial Contraction / Q000502:physiology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000145:classification / Q000502:physiology*; D016276:Ventricular Function
D005456:Fluorescent Dyes; D007211:Indoles; D011942:Receptors, Adrenergic, alpha; C048960:indo-1; D002118:Calcium
L'effetto della stimolazione alpha 1-adrenergica del miocardio dipende dalle azioni opposte dei due sottotipi recettoriali.