Do Mitochondria Participate in General Cardiac Hypertrophy?

Conclusions and summary 1. Left ventricular weight:body weight ratio of a group of hypertensive rats was 55% greater than that of similar group of normotensive rats. 2. Ratio of “non-particulate” proteins of left ventricle to total body weight was 53% greater in hypertensive group than in normotensive group. 3. Mitochondria of left ventricle also participated in cardiac hypertrophy of the hypertensive group. Mitochondrial protein:body weight ratio was 25% greater in hypertensive group than in normotensive group. 4. Sub-mitochondrial particles of left ventricle, smaller in size than the mitochondria, also participated in cardiac hypertrophy. Ratio of protein in these particles to total body weight was 37% greater in hypertensive series than in normotensive series. 5. Hypertrophy of mitochondria, however, was not as great proportionately as that of left ventricle as a whole. Ratio of mitochondrial protein to total left ventricular weight was 19% less in hypertensive rats than in normotensive group. When expressed as ratio of mitochondrial protein to ”non-particulate” protein, the ratio was 17% less in the hypertensive group compared to normotensive group. 6. Hypertrophy of the sub-mitochondrial particles in hypertensive rats was also proportionately less than the hypertrophy of left ventricle as a whole. 7. The mass of protein in individual mitochondrion was slightly less in hypertensive rats than in normotensive group, but the difference was not significant. Total number of mitochondria increased 50% as the left ventricle hypertrophied (p = .08). 8. It seems clear that the total mass of mitochondrial protein in the left ventricle can increase in adaptation to an increase in work load.