Sarcoplasmic reticular and mitochondrial calcium transport in cardiac hypertrophy.

To evaluate changes in Ca2+ transport activities in the cardiac sarcoplasmic reticulum (microsomes) and mitochondria, cardiac hypertrophy was induced in rabbits by constricting the abdominal aorta. The animals showed a stable non-failing left heart hypertrophy between 16-22 weeks after the operation. ATP-dependent Ca2+ uptake and Ca2+ binding activities were depressed in microsomes from hypertrophied rabbits in comparison with sham-operated controls (P less than 0.05). These changes were seen at different concentrations of free Ca2+ (10(-7) to 10(-4)M) and were accompanied by alterations in the phospholipid content of the microsomal fraction. Mitochondrial Ca2+ transport activities and phospholipid content remained unchanged in the hypertrophied heart. The results of this study identify a specific lesion in the sarcotubular membrane and suggest that the depressed Ca2+ transport activity in the microsomal fraction from the hypertrophied myocardium may be due to changes in its phospholipid composition.