[Structure and function of the myocardial cell in various forms of adaptation]

Comparative ultrastructural morphometric and physiological examinations of the rat's myocardium after swimming exercise, hypokinesia and hypobaric hypoxia show concurrence between morphometric and contractility parameters. Differences in the changes of cell organelles in general and of mitochondria and sarcoplasmic reticulum in particular observed in the experimental models of adaptation used provide a basis for making inferences as to different structural reaction patterns of the myocardial cell. Special importance is attached from the functional point of view to changes in the volume and membrane surface density of the longitudinal sarcoplasmic reticulum and in Golgi's apparatus. Different structural reaction patterns suggest different adaptation mechanisms of the myocardial cell.