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 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.
Institute for Biodiagnostics, National Research Council, Winnipeg, Canada. Kupriyanov@ibd.nrc.ca
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Kupriyanov
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Xiang
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Sun
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Jilkina
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D004280:Dobutamine / Q000494:pharmacology; D004837:Epinephrine / Q000502:physiology*; D066298:In Vitro Techniques; D017202:Myocardial Ischemia / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D012414:Rubidium Radioisotopes / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013552:Swine
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D012414:Rubidium Radioisotopes; D004280:Dobutamine; D011433:Propranolol; D000254:Sodium-Potassium-Exchanging ATPase; D004837:Epinephrine