[Protein-energy malnutrition and hypobaric stress effects on ultrastructure of the heart muscle in rats]. / Efecto de la desnutrición calórico-proteica y del estrés hipóxico sobre la ultraestructura del músculo cardíaco de rata.

A model that simulated nutritional and hypoxic stress is discussed. Wistar male adult rats were used in four groups: A1, A2, B1 and B2. A1 and A2 groups were fed with a diet whose composition was: 16% protein, 43% carbohydrate, and 6% lipids. Group B1 and B2 received the same type of diet but was restricted to 70% the amount consumed by groups A1 and A2. All groups were fed for 15 days. After these 15 days, the half of both groups were introduced into an hypobaric chamber simulating an altitude of 3,500 m for two hours. Pieces of the rats hearts were used for biochemical and ultrastructural studies. In group B a dear decrease in the body and the heart weight was observed. Also a decrement of the heart proteins concentration was noticed. On the contrary the mitochondrial proteins increased. These biochemical changes correlate with the ultrastructural changes observed in the same group in which a decrease of the myofibrilles and abnormal configurations of the mitochondria were found. The undemourishment and the hypobaric stress produced an evident alteration in the ultrastructure of the heart.

Ultrastructure of the heart muscle in rats under hypobaric stress and under high NaCl intake.

Cellular metabolic alterations in the heart have been widely investigated under a variety of experimental conditions in which the oxygen supply was diminished. However, there is relatively scarce information about the effect of the reduced food intake and saline loading on the ultrastructural changes occurring in myocardial cells exposed to hypobaric stress during short periods of time. The purpose of the present study was to analyze the effects of hypobaric stress, NaCl intake and undernourishment on the body and heart weights and the ultrastructural changes produced in the rat myocardial cells under these conditions. The body and heart weights in all the experimental groups were determined as well as the total and mitochondrial protein concentrations. A significant decrease in body and cardiac weights was observed in both groups of undernourished animals submitted to hypobaric stress or not. On the other hand, a slight increase in the mitochondrial protein concentration was obtained in the same groups. Cardiac muscle samples were processed for light- and electron-microscopic observations. Few ultrastructural alterations were seen in the experimental groups fed with a standard diet; however, an increase in the mitochondrial size was shown in the rats that received 0.9 and 1.3% NaCl solutions. In the groups of animals with one third of the normal protein-calorie intake, more intense changes were noted; disappearance of the contractile structures, with almost complete extinction of the Z bands, was commonly observed in the rats submitted to hypobaric stress. The ultrastructural alterations seen in the undernourished animals were even more evident, showing generalized damage to the intracellular components.