Capacity of the Terminal Vascular Bed during Normal Growth, in Cardiomegaly, and in Cardiac Atrophy

Vascular capacity representing the terminal vascular bed was determined by albumin 131 I in the rabbit myocardium during normal and pathological growth of the heart. A considerable increase in the vascular capacity in the first postnatal weeks indicated growth of the terminal vascular bed during this period. Highest values were reached in animals approximately 6 weeks old. From this time, vascular capacity gradually decreased in relation to the increase in heart and body weight. The growth rate of the terminal vascular bed was very rapid during the first postnatal weeks and later became slower; no growth was detected in adult and old animals. Growth of the terminal vascular bed during pathological increase in heart weight followed the same trend. In young animals pathological growth of the heart was accompanied by an increase in the capacity of the terminal vascular bed; in adult animals the total capacity remained unchanged. A decrease in heart weight in animals kept on a protein-free diet was characterized by a relatively small vascular capacity.