Myocardial Contractility. II. Effect of Changes in Cardiac Function on the Subcellular Distribution of Calcium in the Isolated Perfused Rat Heart

1972 ◽  
Vol 50 (9) ◽  
pp. 853-859 ◽  
Author(s):  
Charles W. Tomlinson ◽  
Naranjan S. Dhalla
Keyword(s):  
Heart Rate ◽  
Subcellular Distribution ◽  
Rat Heart ◽  
Myocardial Contractility ◽  
Contractile Force ◽  
Tissue Homogenate ◽  
Perfusion Medium ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Frequency Of Stimulation

The effects of changes in heart rate and contractile force due to electrical stimulation, alteration of the temperature of the perfusion medium, and varying degrees of stretch tension on the subcellular distribution of calcium in the isolated perfused rat heart were studied. Increasing the frequency of stimulation from 80 to 320 pulses/min decreased myocardial contractility without appreciable changes in the levels of calcium in the tissue homogenate and heavy microsomal (8000 – 40 000 × g) fraction. On the other hand, mitochondrial (800–8000 × g) calcium content was greater in hearts stimulated at 120 pulses/min than in hearts stimulated at 80 pulses/min; further increase in the frequency of stimulation resulted in a decrease in the level of mitochondrial calcium. Increasing the temperature of the perfusion medium from 25 to 37 °C increased the heart rate and decreased the contractile force without any changes in the levels of calcium in the homogenate or subcellular fractions. Increasing the stretch tension on the hearts from 0 to 5 g increased the developed contractile force and the level of heavy microsomal calcium without changing the heart rate or the levels of calcium in the homogenate and mitochondria. The results do not reveal any cause–effect relationship between changes in heart function and subcellular distribution of calcium.

Subcellular distribution of phosphagens in isolated perfused rat heart

FEBS Letters ◽  
1980 ◽  
Vol 112 (2) ◽  
pp. 273-276 ◽  
Author(s):  
Risto A. Kauppinen ◽  
J.Kalervo Hiltunen ◽  
Ilmo E. Hassinen
Keyword(s):  
Subcellular Distribution ◽  
Rat Heart ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart

Reversible impairment of myocardial contractility due to hypercarbic acidosis in the isolated perfused rat heart

1991 ◽  
Vol 19 (2) ◽  
pp. 218-224 ◽  
Author(s):  
WANCHUN TANG ◽  
MAX HARRY WEIL ◽  
RAÜL J. GAZMURI ◽  
JOE BISERA ◽  
ERIC C. RACKOW
Keyword(s):  
Rat Heart ◽  
Myocardial Contractility ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart

Biochemical Basis of Heart Function. VI. Influence of Cations on Norepinephrine Transport, Storage, and Synthesis in the Isolated Perfused Rat Heart

1972 ◽  
Vol 50 (5) ◽  
pp. 423-431 ◽  
Author(s):  
V. Balasubramanian ◽  
Naranjan S. Dhalla
Keyword(s):  
Rat Heart ◽  
Heart Function ◽  
Adrenergic Nerve ◽  
Spontaneous Release ◽  
Perfusion Medium ◽  
Experimental Conditions ◽  
Biochemical Basis ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Adrenergic Nerve Endings

The effects of Ca2+ (0–5 mM), Mg2+ (0–16 mM), K+ (0–20 mM), and Na+ (0–145 mM) on the uptake, subcellular distribution, and release of exogenously given 3H-norepinephrine were investigated in the isolated perfused rat heart. The uptake of 14C-tyrosine, the synthesis of 14C-catecholamines, and the endogenous levels of norepinephrine were also determined under these experimental conditions. The uptake of 3H-norepinephrine was markedly decreased on perfusing the hearts with media containing low concentrations of Na+. Addition of Ca2+ to the perfusion medium containing Na+ increased the uptake of 3H-norepinephrine while Mg2+ or K+ had no effect. Increasing the concentration of Na+ from 0 to 145 mM in the perfusion medium increased the 3H-label in the granular fraction and decreased it in the soluble fraction whereas Ca2+, Mg2+, or K+ did not show any action. The spontaneous release of 3H-label was not influenced by the presence or absence of Ca2+, Mg2+, or K+ in the medium. On the other hand, the absence of Na+ was found to accelerate the spontaneous release of 3H-label and this effect was further enhanced when Ca2+ was also omitted from the perfusion medium. Increasing the concentrations of Ca2+ or Na+ in the perfusion medium decreased the rate of synthesis of 14C-catecholamincs from 14C-tyrosine whereas Mg2+ and K+ showed no effect. Absence of Na+, but not of K+, Ca2+, or Mg2+, resulted in a decrease in the endogenous level of norepinephrine. The amount of newly synthesized 14C-catecholamines in the perfusate was more on perfusing the hearts with Ca2+-free or Na+-free medium. These results are consistent with the view that Na+ is required for storage as well as uptake of norepinephrine in the adrenergic nerve terminals in the heart. Ca2+ appears necessary for the optimal uptake of norepinephrine due to Na+ and has been shown to inhibit the spontaneous release of norepinephrine due to Na+ lack. In addition, Na+ and Ca2+ reduce the rate of synthesis of catecholamines in the adrenergic nerve endings in the heart.

Location of epicardial pacemaker electrodes and myocardial contractility

1969 ◽  
Vol 47 (3) ◽  
pp. 267-271 ◽  
Author(s):  
G. M. Tremblay ◽  
M. Nahas
Keyword(s):  
Rat Heart ◽  
Myocardial Contractility ◽  
Calcium Concentration ◽  
Cardiac Contractility ◽  
Sprague Dawley ◽  
Perfused Rat Heart ◽  
Isolated Perfused Rat Heart ◽  
Sprague Dawley Rats ◽  
Significant Difference ◽  
Pacemaker Electrodes

Effects of pacing from different epicardial sites on cardiac contractility were studied in the isolated perfused rat heart. An indwelling balloon containing a known volume of saline was used to record intracavitary pressure (LVP), force, and maximum dp/dt during isovolumic paced contraction. Coronary flow was kept constant, and the adequacy of oxygenation was verified by lactate extraction. Forty male Sprague–Dawley rats weighing 250–300 g were divided into two groups, according to the rate of pacing, and stimulated. Pacing from four different epicardial sites failed to show any statistically significant difference in LVP, force, or maximum dp/dt at either different heart rate or calcium concentration. The present study suggests that myocardial contractility in the isolated perfused rat heart is not affected by the pacing site of the epicardial pacemaker.

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