Protein metabolism after unilateral femoral fracture in the rat, and comparison with sham operation.

Urinary excretion of nitrogen, creatinine and N tau-methylhistidine were measured in the rat after unilateral femoral fracture or sham operation. Increased urinary nitrogen excretion occurred in both groups of rats. Cumulative excretion of both nitrogen and N tau-methylhistidine was slightly greater after femoral fracture than after sham operation and this difference agreed quantitatively with loss of muscle protein from the limb with fracture. Sham operation caused no local effect on muscle-protein content and no differences were seen in muscle-protein content between the uninjured hind limb of rats with femoral fracture and either hind limb of sham-operated rats. It was concluded that bone fracture per se does not contribute significantly to the increased urinary nitrogen excretion seen after femoral fracture in the rat; similar changes are produced by equivalent sham operation and any difference between the effects of the two procedures represents local muscle wasting, probably due to disue of the fractured leg.