Key result
Norepinephrine infusion fails to alter adenine nucleotides, indicating they are unnecessary for increased adenosine release.
In well-oxygenated guinea pig hearts, phosphorylation potential is a better predictor of adenosine release than any individual nucleotide or phosphate concentration.
Questions necessity of nucleotide changes for adenosine release; extends metabolic insights in animal models but leaves open human relevance.
The purpose of this study was to examine adenosine release and high-energy phosphate concentrations during norepinephrine (NE) infusion in isolated guinea pig hearts perfused with a physiological salt solution (PSS) containing erythrocytes (RBC). Phosphate concentrations were monitored using 31P-nuclear magnetic resonance spectroscopy while NE was infused at 6 x 10(-10) mol/min. Compared with perfusion with PSS alone, RBC-perfused hearts consumed more oxygen and developed higher left ventricular pressure and first time derivative of left ventricular pressure at lower coronary flow rates. Adenosine release rates were very similar with both perfusates. NE infusion did not produce a decline in ATP concentration ([ATP]) or an increase in calculated [ADP] and [AMP] in RBC-perfused hearts. However, phosphorylation potential ([ATP]/[ADP][Pi]) declined because of increased [Pi]. We conclude that NE infusion does not change adenine nucleotide concentrations in well-oxygenated guinea pig hearts and that changes in nucleotide concentrations are not necessary for increased adenosine release. Phosphorylation potential is a better predictor of adenosine release than any individual nucleotide or phosphate concentration.
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Ning et al. (1992) studied this question. Perfusion with physiological salt solution containing erythrocytes (RBC) and norepinephrine infusion vs. Perfusion with physiological salt solution alone was evaluated on Adenosine release and high-energy phosphate concentrations. Norepinephrine infusion in RBC-perfused isolated guinea pig hearts did not change adenine nucleotide concentrations, indicating changes in nucleotide concentrations are not necessary for increased adenosine release.
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