Muscle and Plasma Amino Acids After Injury

This study is part of an investigation of whether injury is associated with a unique amino acid pattern in muscle and plasma using the total hip replacement as a model for injury. The role of inactivity is examined as a factor in producing the changes observed with injury and associated bed rest. Nineteen preoperative patients and 16 normal subjects received a muscle biopsy following an overnight fast. Blood for plasma amino acids was drawn at the time of the biopsy. Seven patients (Group I) were treated with 90 g/day of dextrose for the first four postoperative days following which a second biopsy was performed. Eight normals were placed on four days of strict bed rest. Four (Group II) received a regular diet and four (Group III) received 90 g of dextrose/day I.V. as the sole nutrient. Both Groups I and III showed increases in valine, leucine, and isoleucine in both muscle and plasma on the postoperative biopsy. The postoperative pattern differed from that observed in either group of normal subjects in that significant decreases occurred in muscle glutamine and histidine, plasma alanine, lysine and glycine. Phenylalanine, tyrosine, methionine and threonine were increased in muscle postoperatively while only phenylalanine was increased in either Group II or III of the normal subjects. Plasma phenylalanine increased in the patients while remaining unchanged in normal subjects. The pattern reported here for the patient group differs from that reported for other catabolic states (uremia, starvation, etc.), as well as inactivity with or without partial starvation. This study suggests that injury in the form of a total hip replacement is associated with a unique amino acid pattern of muscle and plasma which differs from that observed in other catabolic states. Bed rest plus partial starvation causes a pattern with certain similarities but cannot account for the postoperative changes observed.