Beta-receptor sensitization by repeated injections of isoproterenol and by cold adaptation

LeBlanc, J.; Vallières, Julien; Vachon, C.

doi:10.1152/ajplegacy.1972.222.4.1043

Cited by 63 publications

(9 citation statements)

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“…Repeated injection of rats with isoprenaline mimics the repeated stimulation of @-adrenorecptors by natural catecholamines, and also leads to sensitization of @-receptors (LeBlanc et al 1972). Furthermore, the unpublished results from our laboratory (Harri and Tirri) indicate that increased sympathetic activity or a mental stress (an electric shock connected with water drinking) can produce metabolic changes in the heart muscle, very similar to those described above.…”

Section: Discussionsupporting

confidence: 71%

Comparison of the Effects of Physical Exercise, Cold Acclimation and Repeated Injections of Isoprenaline on Rat Muscle Enzymes

Harri

Valtola

1975

Acta Physiologica Scandinavica

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The metabolic effects on rat cardiac and skeletal muscle of a strenous program of swimming, of cold acclimation and of isoprenaline treatment (0.3 mg/kg daily for 5 five-day weeks) were compared. Exercised and cold-exposed rats gained less body weight than did controls or isoprenaline-treated rats. In all treated groups the heart and the intercapular brown adipose tissue hypertrophied. The size of the adrenals increased only in isoprenaline-treated animals. Cold-acclimation and physical training increased and isoprenaline treatment reduced or did not affect the activities of succinate dehydrogenase, malate dehydrogenase and citrate synthase of cardiac muscle. In the skeletal muscle all treatments resulted in increased activities of these enzymes. Of the anaerobic enzymes analysed, only the activity of hexokinase increased in response to the treatements used. This increase was the same in cardiac as in skeletal muscle, but it was significantly greater with isoprenaline-treatment than with training or with cold-acclimation. The activities of lactate dehydrogenase and phosphofructokinase did not differ significantly. All treatments improved cold resistance, but only swimming exercise and cold acclimation significantly increased tolerance to exercise. It is concluded that prolonged stimulation of adrenergic beta-receptors by catecholamines is responsible for the metabolic changes observed.

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Section: Discussionsupporting

confidence: 71%

Comparison of the Effects of Physical Exercise, Cold Acclimation and Repeated Injections of Isoprenaline on Rat Muscle Enzymes

Harri

Valtola

1975

Acta Physiologica Scandinavica

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“…The determination of beta-receptors in the heart of trained animals and polymorphonuclear granulocytes of endurancetrained athletes showed a similar increase in the number of receptors and in affinity (2,9,11,22,23). Consistent with this finding, isoproterenol stimulation of isolated hearts of trained rats as well as of dogs resulted in a more pronounced increase in heart rate than did the stimulation of the organs of untrained animals (19,20,21,23).…”

Section: Discussionsupporting

confidence: 57%

“…In *Supported by the Bundesinstitut für Sportwissenschaft, KUln-Lövenich. this context, a higher sensitivity to sympathetic stimuli is also being discussed (2,9,10,15,22). The isolated hearts of trained rats, for instance, respond to isoproterenol stimulation by a higher increase in heart rate (20).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the Physiologically Hypertrophied Heart to Isoproterenol*

Dickhuth¹,

Theissen²,

Lehmann³

et al. 1987

Int J Sports Med

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Cardiovascular reactions to isoproterenol stimulation (2 and 4 micrograms/min for 12 min each) were evaluated in seven endurance-trained athletes (marathon runners, VO2 max 66.0 +/- 3.7 ml/kg) and seven untrained subjects (VO2 max 54.4 +/- 3.6 ml/kg). At rest and during stimulation, the heart rate, blood pressure as well as one-dimensional (end-diastolic and end-systolic dimensions, shortening fraction) and two-dimensional (end-diastolic and end-systolic volumes, ejection fraction, stroke volume, cardiac output) echocardiographic parameters were determined. The increase in the heart rate of the endurance-trained athletes (28%; 2 micrograms/min) (58%; 4 micrograms/min) was less than in the untrained controls (34%/76%). The blood pressure behaved similarly in both groups. The stroke volume of the endurance-trained subjects rose during stimulation (14%, 4 micrograms/min); the end-diastolic volume remained nearly constant as the end-systolic emptying increased. The stroke volume of the untrained subjects tended to decrease as the end-diastolic and end-systolic volumes were reduced. In absolute terms, the shortening fraction and ejection fraction were identical. Referring to the heart rate, however, they were elevated in the endurance-trained subjects. Hence, under isoproterenol the rise in heart rate was weaker and the increase in ventricular performance seemed to be stronger in the trained subjects compared to the untrained controls. The causes appear to be different regulative effects of the autonomic nervous system on the sinus node and the ventricular myocardium; intrinsic cardiac mechanisms remain to be discussed.

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“…Cardiac hypertrophy can be induced in the rat by chronic administration of norepinephrine (25), epinephrine (26), and isoproterenol, a synthetic P-adrenoceptor agonist (27). In addition, chronic administra-tion of L-thyroxine to rats also results in increased weights of the heart and interscapular brown fat (28,29).…”

Section: Discussionmentioning

confidence: 99%

Effect of a Reduction in Sodium Intake on Cold-Induced Elevation of Blood Pressure in the Rat

Bergen¹,

Fregly²,

Papanek³

1992

Experimental Biology and Medicine

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Chronic exposure of rats to cold (5 degrees C) induces hypertension within 3 weeks. The objective of this study was to determine the effect of treatment with graded levels of dietary NaCl on the induction of hypertension during chronic exposure to cold. Four groups of male rats were used. The first, given a commercial sodium-deficient diet containing 0.30% NaCl, served as the warm-adapted control group. The second, third, and fourth groups were given the same diet containing 0.075%, 0.15%, and 0.30% NaCl, respectively. Because cold-exposed rats ingest approximately twice as much food as warm-adapted controls, this represented half, the same, and twice the amount of NaCl ingested by the control group. The latter three groups were placed in cold air (5 degrees C). All cold-treated groups had an elevation of systolic blood pressure that was proportional to the concentration of NaCl in the diet by the seventeenth week of exposure to cold. Cardiac hypertrophy occurred to the same extent in all cold-exposed groups and was thus unaffected by the NaCl content of the diet or by the extent of elevation of blood pressure. Hence, cardiac hypertrophy during chronic exposure to cold is supported by other factors, possibly by the increased concentration of either norepinephrine or triiodothyronine, or both, which occurs characteristically in rats under these conditions. The results of this experiment suggest that the amount of NaCl ingested daily plays a role in the cold-induced elevation of blood pressure observed in rats.

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Beta-receptor sensitization by repeated injections of isoproterenol and by cold adaptation

Cited by 63 publications

References 0 publications

Comparison of the Effects of Physical Exercise, Cold Acclimation and Repeated Injections of Isoprenaline on Rat Muscle Enzymes

Comparison of the Effects of Physical Exercise, Cold Acclimation and Repeated Injections of Isoprenaline on Rat Muscle Enzymes

Sensitivity of the Physiologically Hypertrophied Heart to Isoproterenol*

Effect of a Reduction in Sodium Intake on Cold-Induced Elevation of Blood Pressure in the Rat

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