This paper presents our research on metabolic and enzymatic changes in the experimental, Isoproterenol-induced (ISO) hypertensive myocardium of rats. We analyze the effects produced by the simultaneous administration of adenosinetriphosphate (fosfobion) (FOS) and Isoproterenol on the changes in the body weight/heart weight ratio, and on the biochemical changes of cardiac metabolism. We studied the following parameters in the myocardium tissue and blood: plasmatic and tissular creatinin-phosphokinase, Na+K+ ATP-ase in the sarcolemma and the sarcoplasmic reticulum, Ca+2 ATP-ase in the mitochondrial membrane, sarcoplasmic reticulum and sarcolemma, as well as plasmatic and tissular lactate. Our data show an increase of heart weight to 939 mg, compared to 752 mg in the control group, while the heart weight/body weight ratio (mg/g), which was 3.8 in the control group, increased to 5.8 in the group to which Isoproterenol (ISO) was administered, and to 5.2 when fosfobion was associated. Investigation of myocardial metabolism has also shown the fact that under the influence of Isoproterenol, plasma creatinin-phosphokinase rises by 20%, while the association of fosfobion reduces it, in the myocardium tissue, down to 73%, in comparison with the values in the control group. Significant changes were found in the myocardium lactate that decreased by 26% under ISO influence, in comparison with normal values, and that decreased by 90% when FOS and ISO were administered together. This study produces arguments about metabolism-induced cardiac changes under the action of ISO and also contributes to the identification of ways that lead to cardiac hypertrophy. The experiment also demonstrates that the ATP-ases responsible for ion transportation across the membrane are actively involved in myocardium hypertrophy. The disturbances occurring in the investigated enzymatic systems are closed related with the myocardial metabolic ones. Fosfobion does not prevent the appearance and development of Isoproterenol-induced myocardial hypertrophy, but diminishes the increase of myocardial lactate produced by this synthesised catecholamine. At the same time, fosfobion significantly decreases the activity of Ca+2 ATP-ase in the plasmalemma and increases the activity of the Na+ - K+ ATP-ase both in the plasmalemma and in the sarcoplasmic reticulum, indirectly favouring the mechanical processes of cardiac myocytes relaxation. The study of the enzymatic activity of Na+K+ and Ca+2 ATP-ases in our experimental conditions contributes to a better understanding of the mechanisms that produce myocardial and coronary disturbances in myocardial hypertrophy.