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  • 1
    ISSN: 1573-7241
    Keywords: plasma catecholamines ; heart catecholamines ; diet restriction ; beta-adrenergic receptors ; heart function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In view of the common practice of dieting for weight reduction, the influence of severe food restriction (about 25% of ad libitum intake) on adrenergic mechanisms was studied. Cardiac norepinephrine and epinephrine concentrations as well as plasma norepinephrine levels, were increased upon feeding a restricted diet to rats for 14 days in comparison with control rats that ingested about 30 g food/day. Bradycardia as well as characteristic electrocardiographic abnormalities, including prolongation of the QRS and QT intervals, were observed in food-restricted rats. Dietrestricted rats did not develop ventricular arrhythmias in response to epinephrine injections as readily as control rats. Depression in both +dP/dt and-dP/dt of the heart in situ as well as reductions in the inotropic responses to epinephtine were evident in diet-restricted rats. Beta-adrenergic binding studies revealed a significant decrease in receptor density, but the dissociation constant for binding was also depressed in the food-restricted rat heart. Downregulation of the beta-adrenergic receptors in the heart may explain the lack of an epinephrine-induced increase in contractile force development as well as arrhythmias in food-restricted rats. These data demonstrate that severe food restriction has marked effects on adrenergic mechanisms and heart function, and thus some caution should be exercised at early periods of this therapy for weight reduction.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7241
    Keywords: plasma catecholamines ; heart catecholamine ; heart function ; diet restriction ; sympathetic activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To examine the relationship between heart function and plasma catecholamines upon food restriction, normal adult rats were fed 12 g or 6 g food/day for 14 days and 12 g food/day for 28 days. Food-restricted rats exhibited bradycardia, hypotension, and decreased rates of cardiac contraction (+dP/dt) as well as relaxation (-dP/dt) at 14 (12 or 6 g food/day) and 28 (12 g food/day) days. Plasma norepinephrine and epinephrine levels were significantly elevated in the 6 g food/day group at 14 days, whereas in the 12 g food/day group, plasma norepinephrine was elevated at 14 days but was significantly decreased at 28 days. Heart norepinephrine and epinephrine concentrations were elevated at both 14 and 28 days of food restriction in the 12 g food/day group as well as at 14 days in the 6 g food/day group. Thus, dietary restriction appears to result in depressed indices of heart function, while the circulating levels of catecholamines were elevated at early states.
    Type of Medium: Electronic Resource
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