Pressure-induced hypertrophy in hearts of dwarf pigs

Myocardial DNA-synthesis has been investigated in five adult dwarf pigs by autoradiography, light and electron microscopy 5, 10, 20, 50 and 100 days after banding the ascending aorta. By the banding procedure the mean ventricular pressure in the left heart rose to 40%, reaching an average of 74% at the time of pulse-labelling with 3H-thymidine. Absolute mean heart weights of the hypertrophic hearts reached 165 +/- 25 g in contrast to ten normal hearts with an average of 69 +/- 8 g. The highest labelling indices were found 10 days after onset of pressure-load: 0.46% in the left ventricular wall, 0.35% in the septum and 0.55% in the right ventricular wall. After 20 to 100 days of aortic constriction the labelling indices ranged from zero to 0.25% indicating a continuous slight DNA-synthesis. Electron micrographs demonstrate activation of the rough endoplasmic reticulum and synthesis of myofilamental and myofibrillar structures, changes of the number and size of mitochondria, the nuclear membrane, as well as changes due to hypoxia and degeneration.