Can exercise promote revascularization in the transition zone of infarcted rat hearts?

1984 ◽  
Vol 62 (6) ◽  
pp. 630-633 ◽  
Author(s):  
K. Przyklenk ◽  
A. C. Groom
Keyword(s):  
Coronary Artery ◽  
Transition Zone ◽  
Recovery Period ◽  
Oxygen Demand ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Voluntary Exercise ◽  
Border Zone ◽  
Normal Number ◽  
Rat Hearts

A border or transition zone, comprising muscle fibers supplied by fewer capillaries than normal, and characterized by an altered capillary – fiber geometry, is present as long as 5 weeks following coronary artery occlusion in the rat. This zone, which extends 225 – 525 μm laterally from the margin of the necrosis, may be at risk of becoming hypoxic, especially under conditions of increased oxygen demand. Our objective was to determine whether exercise can stimulate capillary growth in this transition zone. Myocardial infarcts were induced in rats by ligating the left coronary artery, midway between its origin and the apex of the heart. After a 1-week recovery period, the animals underwent 4 weeks of voluntary exercise, 2 h/day, 6 days/week. Rats which had run a total distance of 5 – 10 km during the month had both a normal number of capillaries and normal capillary–fiber geometry in the transition zone. In contrast, rats that ran either less than 5 km or more than 10 km during the 4 weeks showed no significant improvement in the number of capillaries or capillary – fiber geometry within the border zone. Thus, under certain conditions, exercise can promote revascularization in the transition zone of infarcted rat hearts.

Microvascular evidence for a transition zone around a chronic myocardial infarct in the rat

1983 ◽  
Vol 61 (12) ◽  
pp. 1516-1522 ◽  
Author(s):  
K. Przyklenk ◽  
A. C. Groom
Keyword(s):  
Coronary Artery ◽  
Transition Zone ◽  
Myocardial Infarct ◽  
Muscle Fibers ◽  
Young Male ◽  
Coronary Artery Occlusion ◽  
Capillary Density ◽  
Artery Occlusion ◽  
Male Rats ◽  
Capillary Supply

Muscle fibers in the transition zone of an infarcted heart are thought to be potentially ischemic during the first 6–9 h following coronary artery occlusion. However, the long-term fate of the muscle fibers at the margin of the necrosis is uncertain. Ischemia implies reduced oxygenation, possibly owing to a reduced capillary supply; thus our objective was to determine whether a region of reduced microvascular supply exists at the margin of a necrosis produced by chronic coronary artery occlusion. Five variables were used to quantitate the capillary supply in the transition zone: C/F (capillary to fiber) ratio, Vf (number of vessels around a fiber), Fv (number of fibers surrounding a vessel), capillary density, and fiber diameter. Infarcts were induced in young male rats by ligating the left coronary artery midway between its origin and the apex of the heart. Five weeks later, the capillary supply in the transition zone was significantly below control values, i.e., significant reductions in C/F, Vf, and Fv were found. This region of reduced capillary supply extended 225–525 μm laterally from the edge of the necrosis. Thus, a narrow transition zone, defined as a region of viable muscle fibers with a subnormal microvascular supply, exists as long as 5 weeks following coronary artery occlusion in the rat.

Effects of exercise frequency, intensity, and duration on revascularization in the transition zone of infarcted rat hearts

1985 ◽  
Vol 63 (4) ◽  
pp. 273-278 ◽  
Author(s):  
K. Przyklenk ◽  
A. C. Groom
Keyword(s):  
Transition Zone ◽  
Voluntary Exercise ◽  
Exercise Frequency ◽  
Capillary Supply ◽  
Capillary Growth ◽  
Normal Number ◽  
Rat Hearts ◽  
Exercise Period ◽  
Group B ◽  
Frequency Intensity

In the rat model of chronic myocardial infarction the border or "transition zone," extending 225–525 μm from the margin of the scar, is supplied by significantly fewer capillaries and characterized by an altered capillary-fiber geometry when compared with healthy rat myocardium. Four weeks of daily voluntary running can, under certain conditions, promote capillary growth and a shift in capillary-fiber geometry, such that a normal capillary supply is restored to the transition zone. However, the importance of exercise frequency, intensity, and duration for capillary growth in the transition zone has not been determined. One week after surgical occlusion of the left coronary artery, rats were divided into four groups following different protocols of voluntary exercise (running): A (2 h/day, 6 days/week for 4 weeks), B (2 h/day, 3 days/week for 4 weeks), C (2 h/day, 6 days/week for 2 weeks, followed by 2 weeks sedentary), and D (2 h/day, 6 days/week for 2 weeks). Significant improvements in capillary supply to the transition zone were associated with voluntary exercise, three separate factors being of importance, (i) An intermediate total distance run; rats that ran 5–10 km in the month restored a normal number of capillaries and a normal capillary-fiber geometry in the transition zone, whereas rats that ran either <5 or >10 km showed no significant improvements. (ii) A balance between exercise frequency and mean distance ran per 2-h exercise period; rats in group B (3 days/week) had to run twice the daily distance of those in group A (6 days/week) to obtain the same improvement in capillary supply. (iii) Regular reinforcement of the exercise periods throughout the experiment; animals in groups B and D demonstrated significant increases in capillary supply in the transition zone, while those in group C did not. Although exercise stimulates capillary growth and a shift in capillary-fiber geometry in the transition zone, the mechanisms underlying these improvements are, as yet, unknown.

Regional myocardial blood flow and necrosis in primates following coronary occlusion

1984 ◽  
Vol 246 (4) ◽  
pp. H635-H639 ◽  
Author(s):  
M. Lavallee ◽  
S. F. Vatner
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Myocardial Blood Flow ◽  
Coronary Occlusion ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Border Zone ◽  
Regional Myocardial Blood Flow ◽  
Lateral Border ◽  
Regional Myocardial Blood

The effects of acute coronary artery occlusion on regional myocardial blood flow distribution in the remote nonischemic zone, the central ischemic zone, and the lateral border zone of the infarct were evaluated in conscious primates. Prior to coronary artery occlusion, blood flow was 1.51 +/- 0.11 in endocardial (Endo) and 1.36 +/- 0.11 ml X min-1g-1 in epicardial (Epi) layers with an Endo-to-Epi ratio of 1.17 +/- 0.05. Regional blood flow in the remote nonischemic zone increased by 28.0 +/- 4.7 and 31.7 +/- 3.6% for Endo and Epi layers, respectively, following coronary occlusion and remained elevated during the subsequent 24 h. At the center of infarct, Endo and Epi blood flows were depressed by 97.9 +/- 0.7 and by 97.9 +/- 0.8%, respectively, at 5 min after coronary occlusion and remained severely depressed throughout the 24-h observation period. Blood flow at the ischemic lateral border of the infarct was severely depressed and similar to the flow at the center of the infarct, whereas the nonischemic lateral border of the infarct had blood flow levels similar to the remote, nonischemic myocardium. Microsphere loss was not a feature of the primate infarct.

dl-3-Hydroxybutyrate administration prevents myocardial damage after coronary occlusion in rat hearts

2002 ◽  
Vol 283 (5) ◽  
pp. H1968-H1974 ◽  
Author(s):  
Zhitian Zou ◽  
Shiro Sasaguri ◽  
Katare Gopalrao Rajesh ◽  
Ryoko Suzuki
Keyword(s):  
Coronary Artery ◽  
Infarct Size ◽  
Ischemia Reperfusion ◽  
Myocardial Damage ◽  
Coronary Artery Occlusion ◽  
Artery Occlusion ◽  
Rat Hearts ◽  
High Concentrations ◽  
Myocardial Infarction Size

To investigate the role of high concentrations of dl-3-hydroxybutyrate (DL-3-HB) in preventing heart damage after prolonged fasting, infarct size and the incidence of apoptosis caused by ischemia-reperfusion were determined in four groups of Wistar rats. Fed rats (±DL-3-HB group) and fasted rats (±DL-3-HB group) were subjected to 30 min of left coronary artery occlusion and 120 min of reperfusion. DL-3-HB was administered intravenously 60 min before the coronary artery occlusion. Infarct size, defined by triphenylyetrazolium chloride (TTC) staining, was reduced from 72 ± 3% (fed group), 75 ± 5% (fed + DL-3-HB group), and 70 ± 5% (fasting group), respectively, to 26 ± 4% ( P < 0.01 vs. fasting + DL-3-HB group). Apoptosis, as defined by single-stranded DNA staining, was significantly reduced in the subendocardial region in the fasting + DL-3-HB group (9 ± 2%) compared with the other groups (39 ± 6% in the fed group, 37 ± 5% in the fed + DL-3-HB group, and 34 ± 3% in the fasting group; P < 0.01). In addition, levels of ATP in the fasting + DL-3-HB group were significantly higher compared with other groups after 30 min of ischemia and 120 min of reperfusion ( P < 0.01). In conclusion, the present study demonstrates that high concentrations of DL-3-HB reduces myocardial infarction size and apoptosis induced by ischemia-reperfusion, possibly by providing increased energy substrate to the fasted rat myocardium.

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