Remodelling and functional alterations of the rabbit coronary artery in volume overloaded heart.

Objective: The aim was to study the contractility of the conduit coronary artery to vasoactive agents in developing and established volume overload cardiac hypertrophy and to compare it with structural alterations in the artery.

Methods: Aortic valve insufficiency in rabbits was used to produce a volume overloaded heart. One month (developing hypertrophy), and four months (stabilised hypertrophy) after inducing aortic insufficiency, the isometric contraction of the coronary artery to acetylcholine, serotonin, and potassium chloride was recorded.

[The effect of long-term administration of metipranolol on passive diastolic properties of the hypertrophic ventricle].

In the course of adaptation of the rabbit heart to volume load passive diastolic properties of the hypertrophic ventricle and myocardium were changing significantly. On day 30 following perforation of the aortic valve stiffness of the ventricle was reduced, yet normalized ventricular stiffness and myocardial stiffness were increased. These changes were prevented by beta adrenergic blockade during development of adaptation of the heart to volume load.

[Quantitative ultrastructural characteristics of mitochondria and myofibrils in the myocardium in chronic hemodynamic overload].

Stereological morphometry was used to determine ultrastructural changes of the myocardium in the course of well defined chronic hemodynamic overload. Overload was induced in the hearts of rabbits by perforation of aortic valves. Relative volumes of mitochondria, myofibrils were measured in tissue samples taken from subendocardial and subepicardial region of the left ventricle.

[Passive diastolic properties of the left ventricle during development of cardiac hypertrophy].

Induced insufficiency of the aortal valve in rabbits is followed by gradual adaptation of the heart to volume load. In the period of developing hypertrophy, we studied the changes in the passive diastolic properties of the ventricle. By analyzing the passive relationship between the volume of the ventricular cavity and the intraventricular pressure, the stiffness of the ventricle, normalized ventricular stiffness, and myocardial stiffness were determined.

Constriction ability of coronary artery in volume overload cardiac hypertrophy.

The constrictor response of the rabbit conduit coronary artery from hypertrophied heart (volume-overload stabilized hypertrophy) was studied to vasoactive substances. The heart/body weight ratio was 2.67 +/- 0.

Calcium transport by intracellular membrane structures in the myocardium of hypertrophied and failing hearts.

After inducing haemodynamic cardiac overload in rabbits, the authors studied in several stages (1-14 months) the calcium transport activity of the mitochondrial and sarcoplasmic myocardial fractions using labelled 45CaCl2. A coincidence was found between changes in myocardial contractility and changes in calcium transport activity of intracellular organelles. A possible important role of mitochondria in this adaptive process was also documented.

Respiratory and oxidative phosphorylation of myocardial mitochondria in hypertrophied and failing hearts.

Respiratory and oxidative phosphorylation activity of mitochondria was studied in the course of the adaptation of the heart to haemodynamic overload in rabbit due to aortic valve insufficiency. In the period of developing cardiac hypertrophy, the rate of oxygen consumption in stage 3, i.e.

[The effect of thyroid hormone administration and its exclusion on the development of cardiac hypertrophy in rabbits].

The authors, using rabbits for their experiments (26), studied the effect of application of thyroid hormones (Thyreoiodine Spofa) and that exclusion of these hormones by means of thyroidectomy on the mass of the heart, the concentration of nucleic acids and proteins in the subcellular structures of the heart muscle of intact animals. They observed that administration of hormones of the thyroid gland in a relatively short time led to hyperthrophy of the heart, increased concentration of ribonucleic acid and to modifications of the concentration of proteins in the subcellular structures of the heart muscle. Exclusion of the thyroid hormones, on the other hand, caused a decrease of the mass of the myocardium, decrease concentrations of RNA, DNA and also that of the proteins of the mitochondrial and myofibrillar fractions of the myocardium.

[The effect of exclusion of thyroid hormones on cardiac adaptation to increased work load in rabbits].

The authors studied, in experiments in rabbits (26), the effect of exclusion of thyroid hormones on the formation and evolution of cardiac hypertrophy in animals with artificial insufficiency of the aortic valves. Lack of thyroid hormones due to thyroidectomy, according to the observation of the authors, led to slowing down of the growth of the mass of the heart muscle and to increased concentrations of ribonucleic acid, i. e.