Elevated ammonia release from dystrophic chicken muscle cell and fibroblast cultures

The activity of adenosine monophosphate (AMP)‐aminohydrolase, the major NH 3 ‐producing enzyme in skeletal muscle, was approximately 35% lower in 7‐day dystrophic muscle cell cultures than in normal muscle cells cultures. However, the release rate of NH 3 from dystrophic muscle cells was 45% higher than that from normal muscle cells. The reasons for this apparent discrepancy are not clear. To determine indirectly if deamination of amino acids from protein degradation contributed to NH 3 release, cells were incubated with 100 μg/ml of the protease inhibitor, leupeptin. Leupeptin reduced the rate of NH 3 release by only 18.8% in normal muscle cells and 16% in dystrophic muscle cells. The release of NH 3 was also higher from dystrophic chicken fibroblast cultures.