Effect of metoprolol administration on renal sodium handling in experimental congestive heart failure.
BACKGROUND
Long-term metoprolol therapy improves cardiac performance and decreases mortality in patients with chronic congestive heart failure (CHF). This study examined the effect of long-term metoprolol therapy on renal sodium handling in an experimental rat model of CHF.


RESULTS
Rats with left coronary ligation and myocardial infarction-induced CHF were treated with metoprolol (1.5 mg. kg-1. h-1) or vehicle for 3 weeks by osmotic minipump. They were then evaluated for their ability to excrete a short-term sodium load (5% body weight isotonic saline infusion over 30 minutes) and a long-term sodium load (change from low- to high-sodium diet over 8 days). All CHF rats had left ventricular end-diastolic pressure >10 mm Hg, and heart weight/body weight ratios averaged 0.68+/-0.02% (versus control of approximately 0.40%). Compared with vehicle CHF rats (n=19), metoprolol CHF rats (n=18) had lower basal values of mean arterial pressure (122+/-3 versus 112+/-3 mm Hg) and heart rate (373+/-14 versus 315+/-9 bpm) and decreased heart rate responses to intravenous doses of isoproterenol. During short-term isotonic saline volume loading, metoprolol CHF rats excreted 54+/-4% more of the sodium load than vehicle CHF rats. During long-term dietary sodium loading, metoprolol CHF rats retained 28+/-3% less sodium than vehicle CHF rats.


CONCLUSIONS
Metoprolol treatment of rats with CHF results in an improved ability to excrete both short- and long-term sodium loads.
Department of Internal Medicine, University of Iowa College of Medicine and Veterans Administration Medical Center, Iowa City, Iowa, USA. geradl-dibona@uiowa.edu
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D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D004039:Diet, Sodium-Restricted; D006333:Heart Failure / Q000188:drug therapy / Q000378:metabolism*; D006439:Hemodynamics / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008790:Metoprolol / Q000494:pharmacology* / Q000627:therapeutic use; D009318:Natriuresis / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012982:Sodium, Dietary / Q000493:pharmacokinetics*; D016277:Ventricular Function, Left / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D012982:Sodium, Dietary; D008790:Metoprolol; D007545:Isoproterenol