Effect of hypophosphatemia on muscle metabolism after exercise in pigs

Five Swedish Landrace pigs with a mean weight of 51 +/- 5 kg performed an exercise test on a treadmill at a speed of 1.8 m/s and a duration of 10 min. Hypophosphatemia was then induced in these pigs by addition of aluminium hydroxide (liquid antacid) to the normal feed. After 3 weeks, the exercise test was repeated when the mean weight of the pigs was 65 +/- 9 kg. Five other Swedish Landrace pigs with a mean weight of 72 +/- 4 kg performed a similar exercise test. Muscle biopsies from M. biceps and blood samples were taken from all pigs 3-5 days before and immediately after each exercise test. Hypophosphatemic pigs had significantly lower serum phosphate and higher aluminium levels than normophosphatemic pigs. In all pigs, glycogen content in muscle decreased significantly (-108 to -135 mmol/kg muscle) with exercise while no changes were seen in adenosine triphosphate, creatine phosphate or inorganic phosphate concentrations. In normophosphatemic pigs, glucose-6-phosphate and lactate concentrations increased significantly during exercise by 2-4 mmol/kg and 12.8-14.4 mmol/kg, respectively. However, in hypophosphatemic pigs, glucose-6-phosphate concentrations decreased significantly during exercise by 4.4 mmol/kg and lactate levels were unchanged. These results indicate that low serum inorganic phosphate levels influence muscle metabolism and glycolysis in connection with physical exercise.