[Ultrastructural changes of hypertrophied myocardium in severe experimental hypoxia. Effects of diphosphothiamine and of an antagonist of the vitamin B1. (author's transl)].

The ultrastructural changes occurring in hypertrophic heart cases during severe experimental hypoxia, conducted intermittently for 140 and 250 hours, are reported in the present study. For this purpose, serial right myocardial specimens of control and treated groups of animals were obtained and examined by electron-microscopy. Most areas of the individual myocardial tissue taken during prolonged degrees of exposures to normobaric hypoxia, showed an increased number of mitochondria, their prominent destructive changes, enlargement of cisternae of sarcoplasmic reticulum, reduction and derangement of the cristae and an increase of glycogen and lipif droplets cellular content. Different responses were associated with the various experimental designs which include simple hypoxia, hypoxia with administration of Diphosphothiamine (DPT, 30 mg/hie/Kg body weight) and hypoxia with administration of an antagonist of the vitamin B1, neopyrithiamine (PyTh, 20 mg/die/Kg body weight). Alterations in the fine structure of myocardial cells and cellular organelles could complement the increased glycolitic activity and phospholipid biosynthesis for the compensatory mechanism of the heart to hypoxic stimulus. These changes were most evident in the hypoxic animals treated with PyTh because of a large disturbance of energy production caused by the antivitamin. Most of ultrastructural and glycogen content changes disappeared when DPT was administered to the animals in hypoxia. However, the mitochondria were larger in size and their matrices had higher electron density than in the normal control animals. The significance of the morphological and biochemical findings are discussed.