Calcium is thought to play a major role in the activation of mammalian cardiac muscle. Several investigators have utilized Electron Probe X-ray Microanalysis (EPMA) to study the role of calcium in myocardial contraction. The purpose of this study is to measure subcellular elemental concentrations in rat papillary muscle under the influence of caffeine or elevated extracellular calcium. Of particular interest is the concentration of calcium in the junctional sarcoplasmic reticulum (jSR) under these conditions.Male Sprague-Dawley rats weighing approximately 300 g were anesthetized using I.P. Na-pentabarbitol injection. The hearts were carefully removed and back-perfused with a modified Tyrodes solution via cannulation of the aorta. The wall of the right ventricle was cut away revealing the papillary muscles. The tendon and wall ends of the papillary muscle were then sutured and the muscle was carefully cut out of the heart. The papillary muscle was then placed on the freezing device holder and the suture tied to a fixed post and tension transducer post, as shown in Figure 1.
