CHANGES IN DIETARY-PROTEIN INTAKE FAIL TO PREVENT DECREASE IN MUSCLE GROWTH INDUCED BY SEVERE HYPOXIA IN RATS

Muscle growth, fiber size, muscle and liver glycogen, plasma hormones, and muscle glutamine concentration were evaluated in rats chronically exposed (26 days) to a simulated hypobaric altitude (HA; 6,000 m) and fed diets of varying protein concentrations (10, 20, or 40 g protein/ 100 g of dry matter; LP, MP, and HP, respectively). Values were compar ed with those measured in animals maintained under normobaric conditio ns and either fed ad libitum (SL groups) or pair fed equivalent quanti ties of food consumed by HA animals (PF groups). There was marked anor exia in response to HA exposure for all protein diets (P < 0.001). A s pecific effect of hypoxia on the decrease in muscle growth has been id entified by comparison of the values of the muscle weight-to-body weig ht ratio between HA and PF groups (P < 0.05 for all dietary protein le vels). Plasma insulin concentrations were lower in HA than in SL and P F rats (P < 0.05). Liver glycogen was significantly decreased by expos ure to HA (P ( 0.001) and high dietary protein content (P < 0.005). Hy poxia per se and decreased food intake had additive effects on soleus muscle glycogen concentrations. An increase in muscle glutamine was ob served in rats fed the LP diet in comparison with the MP diet, especia lly in SL and PF groups (P < 0.05). These results clearly demonstrate that 1) hypobaric hypoxia per se decreases growth rate in rats and 2) increasing the dietary protein intakes in rat had no effect on the dep ression of muscle growth related to high altitude but had deleterious effects on glycogen deposition in liver and fast muscle.