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Myocardial potassium uptake during alpha- and beta-adrenoceptor stimulation
O Ellingsen1, O A Vengen, A Ilebekk
1Institute for Experimental Medical Research, Ullevaal Hospital, University of Oslo, Norway.
The American Journal of Physiology
|October 1, 1987
Summary
Both alpha- and beta-adrenoceptor stimulation increase myocardial potassium uptake. Beta-stimulation by isoproterenol resulted in greater potassium uptake than alpha-stimulation by phenylephrine.
Area of Science:
- Cardiology
- Physiology
- Pharmacology
Background:
- Adrenoceptors play a crucial role in regulating cardiac function.
- Understanding the impact of adrenoceptor stimulation on myocardial ion balance is vital for cardiovascular research.
Purpose of the Study:
- To compare the effects of alpha- and beta-adrenoceptor stimulation on myocardial potassium (K+) balance.
- To investigate the role of the Na-K pump in mediating these changes.
Main Methods:
- Anesthetized open-chest pigs underwent intracoronary infusions of isoproterenol (beta-agonist) and phenylephrine (alpha-agonist).
- Myocardial K+ balance was assessed by measuring K+ concentrations in arterial and coronary sinus blood using catheter-valinomycin minielectrodes.
- Computerized data analysis calculated the arterial-coronary sinus difference and accumulated myocardial K+ uptake.
Main Results:
- Isoproterenol caused a significant transient decrease in coronary sinus K+ and substantial myocardial K+ uptake.
- Phenylephrine, after beta-blockade, induced a smaller reduction in coronary sinus K+ and less myocardial K+ uptake compared to isoproterenol.
- Neither stimulation led to indicators of cardiac ischemia, such as altered O2 extraction or lactate uptake.
Conclusions:
- Both alpha- and beta-adrenoceptor stimulation stimulate myocardial K+ uptake, likely via enhanced Na-K pump activity.
- Beta-adrenoceptor stimulation is more effective in inducing myocardial K+ uptake than alpha-adrenoceptor stimulation.