Effect of adrenergic stimulation on Rb(+) uptake in normal and ischemic areas of isolated pig hearts: (87)Rb MRI study

The role of adrenergic stimulation in Rb(+) uptake in normal and ischemic areas of pig hearts was investigated using an agonist (dobutamine) and an antagonist (S-propranolol). The left anterior descending artery (LAD) in isolated pig hearts was cannulated to maintain adequate perfusion of the LAD be...

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Bibliographic Details
Published in:Magnetic resonance in medicine 2002-07, Vol.48 (1), p.15-20
Main Authors: Kupriyanov, V V, Xiang, B, Sun, J, Jilkina, O
Format: Article
Language:English
Subjects:
Adrenergic beta-Agonists - pharmacology
Adrenergic beta-Antagonists - pharmacology
Animals
Dobutamine - pharmacology
Epinephrine - physiology
In Vitro Techniques
Myocardial Ischemia - metabolism
Propranolol - pharmacology
Rubidium Radioisotopes - metabolism
Sodium-Potassium-Exchanging ATPase - metabolism
Swine
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Summary:The role of adrenergic stimulation in Rb(+) uptake in normal and ischemic areas of pig hearts was investigated using an agonist (dobutamine) and an antagonist (S-propranolol). The left anterior descending artery (LAD) in isolated pig hearts was cannulated to maintain adequate perfusion of the LAD bed (2.2-2.8 ml/min/g). Rb(+) loading was initiated by switching perfusion to Rb(+)-containing Krebs-Henseleit (KH) buffer in the presence of 0.1 microM dobutamine, 0.5 microM propranolol, or no drug (control), and the LAD flow was reduced to 10% of the baseline for 120 min. The flow through the LAD was then restored to normal and the drugs were removed. In all groups the rate of Rb(+) uptake obtained from serial (87)Rb images was severely depressed in the ischemic anterior wall relative to that in the normal posterior wall. Dobutamine increased the rate of Rb(+) uptake in the posterior wall (6.3% +/- 1.4% vs. 2.5% +/- 0.25% per minute in control) and did not affect the rate in the anterior wall (0.86% +/- 0.40% vs. 1.14% +/- 0.19% per minute in control). Propranolol did not affect Rb(+) uptake in either of these areas. We conclude that the stimulation of Rb(+) uptake by dobutamine is related to activation of Na(+)/K(+) ATPase and passive Na(+) influx in normal tissue. The lack of any effect of propranolol implies a low level of endogenous norepinephrine during low-flow (LF) ischemia.
ISSN:0740-3194
DOI:10.1002/mrm.10187