Effect of physical training on calcium transport by rat cardiac sarcoplasmic reticulum

Cardiac microsomes enriched in fragmented sarcoplasmic reticulum (SR) were isolated from hearts of physically trained rats and were compared to those from sedentary rats. Preparations from conditioned rats were found to transport calcium to a greater extent than those from sedentary rats both in the absence and in the presence of 1 mM oxalate. Higher oxalate concentrations abolished the differences in calcium accumulation by cardiac microsomes from conditioned and sedentary rats and indicated a qualitative change in SR from conditioned hearts. We conclude that the increased transport by SR from hearts of conditioned rats may provide one mechanism for enhanced contractile reserve in these hearts.