Prospects of X-ray microanalysis in the study of pathophysiology of myocardial contraction.

X-ray microanalysis was used to compare chemically untreated cryosections of quick-frozen myocardial tissue in "caffeine contracture" with cryosections of normal muscle. Our goal was to find out if it is possible by means of this method to detect changes in the calcium compartmentalization of the myocardial cell occurring by changes in its functional state. While it is possible to quantitate calcium in the cisternae of sarcoplasmic reticulum of the control muscle preparation, calcium could never be detected in these compartments of caffeine-contracted muscles. In active microsomal fraction of ventricular myocardium it is possible to quantitate calcium and also to distinguish two components on account of their different ability to accumulate this element. The calcium content is different in the two components of the fraction.