Sarcoplasmic reticular Ca2+-pump adaptation in cardiac hypertrophy due to pressure overload in pigs

Ca2+-transport activities of the sarcoplasmic reticulum isolated from the non-failing hypertrophied left ventricle due to supravalvular banding of aorta for 4 and 8 weeks in pigs were compared with those from the sham operated controls. The rate of Ca2+-uptake, but not the capacity, in 4 weeks hypertrophied heart preparations was increased. On the other hand, both the rate and capacity of sarcoplasmic reticulum to accumulate Ca2+ were decreased at 8 weeks of heart hypertrophy. The Ca2+-binding and Ca2+-stimulated Mg2+ dependent ATPase activities of the reticular fractions from 4 and 8 weeks hypertrophied hearts were not significantly different from the control values. No changes in the sarcoplasmic reticular phospholipid contents were evident except that sphingomyelin was significantly decreased in 4 weeks and diphosphatidylglycerol was increased in both 4 and 8 weeks hypertrophied preparations. These results suggest that adaptation of the sarcoplasmic reticulum function in physiologic and pathologic hypertrophied hearts may occur by changing the efficiency of Ca2+-pump system during the development of cardiac hypertrophy.