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KMID : 0360419730090010001
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Korean Journal of Pharmacology
1973 Volume.9 No. 1 p.1 ~ p.21
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Experimental Studies on Cardiac Catecholamine Content
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Abstract
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During the last decade extensive studies on catecholamines have evolved new knowledge in the physiology and biochemistry of adrenergic mechanism. Cardiac muscle, receiving adrenergic fibres from the stellate, cervical and thoracic ganglia, has been repeatedly shown to have a specific capacity to uptake and to store catecholamines. The catecholamine stores in cardiac muscle have also been shown to be important sites for the action of numerous drugs. Under normal condition, a certain level of catecholamines is maintained in the stores and serves as the basis for studying the changes in the catecholamine content of the heart. Because myocardial catecholamines play such important role in the patho-physiology of the heart, it would be interesting to compare the normal level of myocardial catecholamines among various species of animals. An occasional study has dealt with myocardial catecholamines of several species and ages of animals but these have been insufficiently comprehensive to afford a basis for an understanding of the importance of these amines as related to species and ages. The present investigation was undertaken to determine whether or not there is any significance of myocardial catecholamines in the course of the evolution and development of animals. Seasonal changes, sex difference and regional and subcellular distribution of myocardial catecholamines were also examined. The concentration of cardiac catecholamines was determined by the spectrophotofluorometric procedure described by Shore and Olin.
The results obtained were summarized as follows:
1. As animals phylogenetically progressed larger amounts of catecholamines were present in their hearts. A negligibly small amount of catecholamine was present in the hearts of the clam, a nonvertebrate. Among the vertebrates, cold-blooded animals (snake, turtle, frog, eel and fish) had less myocardial catecholamines than warm-blooded animals, of which aves (fowl and duck) had less than mammalia (cat, dog, rabbit, rat, cow and pig). The ratio of norepinephrine to epinephrine also was greater as the animals progress phylogenetically.
2. Examination of the regional distribution of cardiac catecholamines in warm-blooded animals showed that the content of the auricle was generally higher than that of the septum and considerably than that of the ventricle, but the differences of contents among these regions were not so marked.
3. In the embryonic chick, cardiac catecholamines were firstly detected on the 4th day of incubat ion, the time before the cardiac innervation of sympathetic nerves.
The concentrations of these catecholamines increased but not markedly on the 6th day of incubation, soon after the innervation of sympathetic nerves to the heart. The level of the cardiac catecholamines fluctuated throughout the remainder of embryonic development.
4. In newborn rat hearts, a considerable amount of catecholamines was present. With the development of the rats, the concentrations of myocardial catecholamines increased. The ratio of epinephrine and norepinephrine fluctuated within the range of 40 to 60 pervent. However, as development progressed, the percentage of norepinephrine continued to rise, attaining the adult value of 80~90% after 45~60 days. In contrast, the total amount of epinephrine remained fairly constant throughout the animal´s development.
5. No significant sexual differences were observed in the concentration of myocardial catecholamines in the developing rat.
6. The catecholamines in the rabbit hearts increased during the summer season (from May to August) and maintained a fairly constant level in the other seasons of the year.
7, The subcellular distribution of cardiac catecholamines was examined by differential centrifugation of homogenates of cardiac muscles in rabbits, cats and rats. The catecholamines were found to be present approximately 20% in particles of mitochondrial fraction, 45% in particles of microsomal friction and 35% in soluble supernatant fraction. The particle containing catecholamines in cardiac muscle appears to be two different sizes.
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