Effect of isoproterenol on phosphorylase activation in the hyperthyroid rat heart

1979 ◽  
Vol 57 (6) ◽  
pp. 567-573 ◽  
Author(s):  
Penelope A. Longhurst ◽  
John H. McNeill
Keyword(s):  
Blood Flow ◽  
Coronary Blood Flow ◽  
Time Dependent ◽  
Force Of Contraction ◽  
Phosphorylase Activity ◽  
Isolated Atria ◽  
Langendorff Hearts ◽  
The Right ◽  
Dose Dependent Increase ◽  
Dose Dependent

Pretreatment of rats for 3 days with triiodothyronine produced an increase in rate in the right atrium and a decrease in force of contraction in the right ventricle and Langendorff heart.Isoproterenol administration produced a time-dependent increase in rate and tension. The increase in rate was consistently greater in atria from hyperthyroid rats, and the increase in tension consistently greater in tissues from euthyroid rats. Isoproterenol also produced a time- and dose-dependent increase in phosphorylase a activity. In the isolated atria and ventricles enzyme activity was similar in the two groups. In the Langendorff hearts, however, there was an enhancement of the isoproterenol-induced increase in phosphorylase activity in hearts from hyperthyroid rats. Reduction of the coronary blood flow to the level found in euthyroid animals did not reduce the potentiation of phosphorylase activation found in hearts from hyperthyroid rats.It is concluded that the potentiation of phosphorylase activation in hearts from hyperthyroid rats is not due to the increase in coronary blood flow.

Is Calcium a Coronary Vasoconstrictor In Vivo? 

1998 ◽  
Vol 88 (3) ◽  
pp. 735-743 ◽  
Author(s):  
George J. Crystal ◽  
Xiping Zhou ◽  
Ramez M. Salem
Keyword(s):  
Blood Flow ◽  
Oxygen Consumption ◽  
Coronary Blood Flow ◽  
Myocardial Oxygen Consumption ◽  
Extraction Ratio ◽  
Oxygen Extraction ◽  
Oxygen Extraction Ratio ◽  
Myocardial Oxygen Extraction ◽  
Dose Dependent

Background Calcium produces constriction in isolated coronary vessels and in the coronary circulation of isolated hearts, but the importance of this mechanism in vivo remains controversial. Methods The left anterior descending coronary arteries of 20 anesthetized dogs whose chests had been opened were perfused at 80 mmHg. Myocardial segmental shortening was measured with ultrasonic crystals and coronary blood flow with a Doppler flow transducer. The coronary arteriovenous oxygen difference was determined and used to calculate myocardial oxygen consumption and the myocardial oxygen extraction ratio. The myocardial oxygen extraction ratio served as an index of effectiveness of metabolic vasodilation. Data were obtained during intracoronary infusions of CaCl2 (5, 10, and 15 mg/min) and compared with those during intracoronary infusions of dobutamine (2.5, 5.0, and 10.0 microg/min). Results CaCl2 caused dose-dependent increases in segmental shortening, accompanied by proportional increases in myocardial oxygen consumption. Although CaCl2 also increased coronary blood flow, these increases were less than proportional to those in myocardial oxygen consumption, and therefore the myocardial oxygen extraction ratio increased. Dobutamine caused dose-dependent increases in segmental shortening and myocardial oxygen consumption that were similar in magnitude to those caused by CaCl2. In contrast to CaCl2, however, the accompanying increases in coronary blood flow were proportional to the increases in myocardial oxygen consumption, with the result that the myocardial oxygen extraction ratio remained constant. Conclusions Calcium has a coronary vasoconstricting effect and a positive inotropic effect in vivo. This vasoconstricting effect impairs coupling of coronary blood flow to the augmented myocardial oxygen demand by metabolic vascular control mechanisms. Dobutamine is an inotropic agent with no apparent direct action on coronary resistance vessels in vivo.

Cardiac effects of injections of epinephrine into the spinal intermediolateral column

1993 ◽  
Vol 265 (2) ◽  
pp. H633-H641 ◽  
Author(s):  
V. K. Malhotra ◽  
A. Kachroo ◽  
H. N. Sapru
Keyword(s):  
Adrenergic Receptors ◽  
Cardiovascular Responses ◽  
Spinal Level ◽  
Cardiac Effects ◽  
Alpha Adrenergic Receptors ◽  
Small Doses ◽  
The Right ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Stimulation Of

Small doses of epinephrine (0.008, 0.05, and 0.1 pmol, i.e., 20-nl volumes of 0.40, 2.5, and 5 microM solutions) produced a dose-dependent increase in heart rate when micro-injected into the right intermediolateral column (IML) at T2 spinal level. These effects were mediated via alpha 1-adrenergic receptors because prazosin blocked them. The presence of alpha 1-adrenergic receptors at this site was confirmed by microinjections of phenylephrine (a specific agonist for these receptors); phenylephrine elicited tachycardia. Larger doses of epinephrine (320, 2,000, and 3,200 pmol, i.e., 20-nl volumes of 16, 100, and 160 mM solutions) caused bradycardia when microinjected into the IML. These effects were mediated via alpha 2-adrenergic receptors because idazoxan blocked them. The presence of alpha 2-adrenergic receptors at this site was confirmed by microinjections of clonidine (a specific agonist for these receptors); clonidine elicited bradycardia. Injections of the vehicle (20 nl of normal saline containing 0.3% ascorbic acid, pH 7.4) did not evoke a response. Epinephrine, prazosin, or idazoxan did not alter the responses to L-glutamate. None of the doses of epinephrine elicited any response when injected intravenously. The aforementioned results provide pharmacological evidence for the presence of alpha 1- and alpha 2-adrenergic receptors in the IML at T2. Thus a basis is provided for investigating the role, if any, of alpha-adrenergic receptors in the IML in mediating cardiovascular responses elicited by the stimulation of different brain stem areas.

Acute central effects of L-glutamate in pentobarbital-anesthetized dogs

1987 ◽  
Vol 252 (3) ◽  
pp. R594-R598
Author(s):  
J. E. Chelly ◽  
M. F. Doursout ◽  
J. P. Buckley
Keyword(s):  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Dose Effect ◽  
Central Effects ◽  
Intravenous Injections ◽  
Induced Hypertension ◽  
Anesthetized Dogs ◽  
The Right ◽  
Dose Dependent Increase ◽  
Dose Dependent

Microinjections of L-glutamate (10(-10) to 2 X 10(-8) mol/kg) into the nucleus of tractus solitarii produced a dose-dependent increase in mean arterial pressure and a decrease in heart rate. L-Glutamate-induced hypertension was prevented by spinal transection and pretreatment with atropine (1 mg/kg iv) reversed the bradycardia. L-Glutamate also produced a dose-dependent increase in mean arterial pressure when injected intravenously and into the cisterna magna, but the dose-effect curves were shifted to the right. Finally, pretreatment with hexamethonium (30 mg/kg iv) abolished the hypertension resulting from intravenous injections of L-glutamate. These data demonstrate that the nucleus of tractus solitarii may play a determinant role in the central pressor effects of L-glutamate. In addition, we demonstrated that this hypertension was due to a central sympathetic stimulation and that the autonomic nervous system also mediated the pressor effects of intravenous L-glutamate.

Dose-Dependent Effects of Meclofenamate on Peripheral Vasculature of Conscious Rabbits

1983 ◽  
Vol 64 (5) ◽  
pp. 471-474 ◽  
Author(s):  
R. A. Banks ◽  
L. J. Beilin ◽  
J. Soltys
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Organ Blood Flow ◽  
Hepatic Circulation ◽  
Peripheral Vasculature ◽  
Conscious Rabbits ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
The Brain ◽  
Intravenous Sodium

1. Changes in systemic haemodynamics and organ blood flow were measured in conscious rabbits after various doses of intravenous sodium meclofenamate, an inhibitor of prostaglandin cyclo-oxygenase. 2. Meclofenamate had no effect on arterial pressure or cardiac output but caused a dose-dependent fall in renal blood flow. 3. Meclofenamate also reduced adrenal perfusion but, in contrast, caused a dose-dependent increase in blood flow to the brain, bronchial and hepatic circulation and to the testis. No effect was demonstrated on other organs studied. 4. The effect on the cerebral circulation was observed at the lowest dose of meclofenamate (0.75 mg/kg). Higher total doses were necessary for an effect on the renal and bronchial (3 mg/kg) and testicular and hepatic arteries (6 mg/kg). 5. The results suggest a variety of local vasomotor influences of renal and non-renal prostaglandins in conscious rabbits.

Effect of hypoxemia and hypercapnia on regional distribution of myocardial blood flow

1965 ◽  
Vol 208 (6) ◽  
pp. 1211-1216 ◽  
Author(s):  
William D. Love ◽  
Myra D. Tyler
Keyword(s):  
Blood Flow ◽  
Left Ventricle ◽  
Right Ventricle ◽  
Coronary Blood Flow ◽  
Regional Distribution ◽  
Fick Principle ◽  
The Right ◽  
Isotope Content ◽  
Coronary Sinus Blood ◽  
Normal Difference

The effect of hypoxia and hypercapnia on regional coronary blood flow and vascular resistance (CVR) was studied in dogs without thoracotomy. Gas tensions were varied by ventilation at controlled rates with gas mixtures containing 4–100% O2 and 0–24% CO2. After 10 min intravenous infusion of Rb86, the animals were killed and the heart isotope content determined. Blood flow to the left ventricle was calculated by the Fick principle from the isotope uptake and the mean difference in radioactivity of arterial and coronary sinus blood. Patterns of flow elsewhere were estimated from the rates of regional Rb86 clearance. Myocardial Rb86 clearance in the right and left ventricles has been previously shown to be closely related to the rate of coronary blood flow. Hypoxemia and severe hypercapnia (pCO2 above 100 mm Hg) both produced a profound fall in CVR. With hypoxemia this decrease was more marked in the right ventricle. Elevation of pCO2 exaggerated the normal difference in Rb86 uptake between inner and outer thirds of the wall of the left ventricle, while hypoxemia reversed the normal gradients. Hypercapnia did not affect these gradients in the right ventricle, but hypoxemia significantly reduced them.

Effects of intrarenal adenosine on renal function and medullary blood flow in the rat

1988 ◽  
Vol 255 (6) ◽  
pp. F1230-F1234 ◽  
Author(s):  
M. Miyamoto ◽  
Y. Yagil ◽  
T. Larson ◽  
C. Robertson ◽  
R. L. Jamison
Keyword(s):  
Blood Flow ◽  
Sodium Excretion ◽  
Systemic Circulation ◽  
Urinary Flow ◽  
Medullary Blood Flow ◽  
Vasa Recta ◽  
Potent Vasodilator ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Higher Doses

Adenosine is a potent vasodilator of the systemic circulation. Infusion of adenosine into the aorta causes water and sodium retention and a fall in glomerular filtration rate and renal blood flow. The effect of adenosine on medullary blood flow is unknown. Because systemic vasodilatory effects may confound its renal actions, adenosine was infused into the renal artery of anesthetized Munich-Wistar rats at doses of 2, 6, and 15 micrograms/min. A marked dose-dependent increase in urinary flow and sodium excretion was observed. Inulin and p-aminohippuric acid clearance did not change significantly. Blood flow in vasa recta in the exposed renal papilla, as determined by fluorescence videomicroscopy, increased significantly only with the highest dose of adenosine. In control animals infused with the vehicle only, there was no change in any of the above variables. These results indicate that direct intrarenal infusion of adenosine in the rat increases urinary flow and sodium excretion and at higher doses also increases vasa recta blood flow. The effects on urinary flow and sodium excretion were therefore mediated by a mechanism other than an increase in vasa recta blood flow.

Analysis of blood flow in the entire coronary arterial tree

2005 ◽  
Vol 289 (1) ◽  
pp. H439-H446 ◽  
Author(s):  
N. Mittal ◽  
Y. Zhou ◽  
C. Linares ◽  
S. Ung ◽  
B. Kaimovitz ◽  
...  
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Coronary Blood Flow ◽  
Flow Distribution ◽  
Model Parameters ◽  
Coronary Perfusion ◽  
Arterial Tree ◽  
Circumflex Artery ◽  
Left Circumflex Artery ◽  
The Right

A hemodynamic analysis of coronary blood flow must be based on the measured branching pattern and vascular geometry of the coronary vasculature. We recently developed a computer reconstruction of the entire coronary arterial tree of the porcine heart based on previously measured morphometric data. In the present study, we carried out an analysis of blood flow distribution through a network of millions of vessels that includes the entire coronary arterial tree down to the first capillary branch. The pressure and flow are computed throughout the coronary arterial tree based on conservation of mass and momentum and appropriate pressure boundary conditions. We found a power law relationship between the diameter and flow of each vessel branch. The exponent is ∼2.2, which deviates from Murray’s prediction of 3.0. Furthermore, we found the total arterial equivalent resistance to be 0.93, 0.77, and 1.28 mmHg·ml−1·s−1·g−1 for the right coronary artery, left anterior descending coronary artery, and left circumflex artery, respectively. The significance of the present study is that it yields a predictive model that incorporates some of the factors controlling coronary blood flow. The model of normal hearts will serve as a physiological reference state. Pathological states can then be studied in relation to changes in model parameters that alter coronary perfusion.

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