Free amino acid concentrations in spinal tissue from patients dying of motor neuron disease

Because some investigators have reported abnormal concentrations of amino acids (AA) in fluids and tissues of patients with motor neuron disease (MND), we examined the AA content of frozen anterior horn spinal cord tissue taken from seven patients dying of MND and compared the results with those found in 12 control patients. Ammonia (21 +/- 8.1 vs. 12.7 +/- 6.9 mumol/g, P = 0.036) and ornithine (0.41 +/- 0.3 vs. 0.16 +/- 0.09, P = 0.036) were elevated in spinal tissue of motor neuron disease patients. Correlation analysis showed ammonia levels inversely related to duration of illness (r = -0.714, P = 0.036). We concluded that metabolic abnormalities exist in MND. Ammonia and ornithine may be adversely affecting motor neuron function, or alternatively they could be metabolic markers of a more generalized energy-deficient state in motor neuron disease.