Mitochondrial function in canine experimental cardiac hypertrophy

Concentric left ventricular hypertrophy was produced in puppies by coarcation banding of the aorta at age 7 weeks. Hemodynamic, morphologic and biochemical studies were carried out 18 months after the operation. Systolic blood pressure proximal to the aortic constriction was 216 ± 16 mmHg in experimental dogs compared with 115 ± 5 mmHg in littermate control dogs. Ejection fraction of control and experimental dogs were 59 ± 4 and 64 ± 7, respectively. The left ventricular end-diastolic pressure was 6.0 ± 0.4 in control and 8.4 ± 1.1 in experimental dogs. There was no sign of overt heart failure in the experimental dogs. Anatomical analysis of different regions of the heart indicated that LV mass in the experimental dogs was increased by about 60%. Ultrastructure of mitochondria in situ, as observed under electron microscope, was normal both in control and hypertrophic hearts. Mitochondria isolated from epicardial and endocardial regions of the stable hypertrophic hearts showed normal rates of respiration, phosphorylation, citrate synthase, and cytochrome c oxidase activities compared to those isolated from hearts of littermate control dogs. It was, therefore, concluded that mitochondrial function is adequately preserved to meet the increased demand for energy in this model of stable cardiac hypertrophy of long duration.