ABSTRACT. The aim of this collaborative study was to normalized by therapy, the levels of the catabolites of investigate whether guanidino compound analyses in the arginine are still elevated. (Pediatr Res 27: 297-303,1990) biologic fluids can be used as a complementary diagnostic parameter for hyperargininemia. Guanidino compounds were determined in the biologic fluids of all known living hyperargininemic patients using a cation exchange chromatographic system with a fluorescence detection method. The serum arginine, homoarginine, a-keto-6-guanidinoDeficiency of arginase, the last enzyme of the urea cycle, leads valeric acid, argininic acid, and N-a-acetylarginine levels to hyperargininemia. The first clinical and biochemical descripof all the hyperargininemic patients are higher than the tions of two sisters affected with hyperargininemia were pubnormal range. Similar increases were seen for the urinary lished in 1969 (1) and 1970 (2, 3). Five y later, another sister was excretion of a-keto-6-guanidinovaleric acid and argininic diagnosed shortly after birth (4). Since then, 19 other cases from acid. Untreated hyperargininemic patients have the highest 17 families have been reported (5-22). Patients with hyperargiguanidino compound levels in cerebrospinal fluid. How-ninemia present a neuropsychiatric syndrome consisting of varyever, even under therapy, the arginine, homoarginine, a-ing degrees of mental retardation, epilepsy, and progressive spasketo-6-guanidinovaleric acid, and argininic acid levels in ticity. This latter symptom is at variance with other defects of cerebrospinal fluid are still increased. Protein restriction the urea cycle. Some patients have, in addition, recurrent epialone is not sufficient to normalize the hyperargininemia, sodes of vomiting and irritability accompanied by moderate but protein restriction together with supplementation of hyperammonemia. As a consequence of the arginase deficiency, essential amino acids with or without sodium benzoate the patients accumulate excessive arginine. Some secondary cadecreases further the arginine levels. However, whereas tabolites of arginine, guanidino compounds, are massively exthe argininemia can be normalized, the catabolites of ar-creted in the urine of these patients (23). Figure 1 shows some ginine are still increased. We conclude that the urinary proposed catabolic pathways of arginine in patients with hyperamino acid levels may remain normal in hyperargininemia, argininemia. whereas consistent increases of the guanidino compounds In hyperargininemia it is unclear whether ammonia is the are observed. Thus, guanidino compound analyses can be principal toxin. Indeed, the presence of normal or only slightly used as a complementary biochemical diagnostic parameter elevated ammonia levels has been demonstrated in several pafor hyperargininemia. Although the argininemia can be tients (6,7,9,15), and the progressive spasticity typically en-

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Argininemia is an autosomal recessive disorder caused by a deficiency in the liver-type arginase enzyme. Clinical manifestations include progressive spastic diplegia and mental retardation. While the quality of life can severely deteriorate in most such patients, some do show remarkable improvement in neurological symptoms while on controlled diets. We examined the thesis that differences in clinical responses to dietary treatment are based on molecular heterogeneity in mutant arginase alleles. Genomic DNAs from 11 patients with argininemia were examined using the polymerase chain reaction, cloning, and sequencing. Nine mutations representing 21/22 mutant alleles were identified in 11 patients with argininemia, and four of these mutations were expressed in vitro to determine the severity of enzymatic defects. We found that these mutations accounted for 64% of the mutant alleles in our patients. Based on findings in vitro expression tests, the mutations can be considered either severe or moderate. Patients with at least one moderate mutant allele responded well to dietary treatment; concentrations of plasma arginine were controlled within 300 microM. In contrast, patients with two severely mutated alleles did not respond to dietary treatment and plasma arginine was over 400 microM. Argininemia is heterogeneous at the molecular level. The degree of clinical improvement during dietary treatment is reflected in the concentration of arginine in plasma, as a measure of metabolic control. Plasma arginine levels during treatment is reflected in the concentration of arginine in plasma, as a measure of metabolic control. Plasma arginine levels during treatment correlated with types of molecular defects in the arginase genes.

ExtractThe changes in plasma aminogram prcduced by variations in level of protein intake provided either as whole protein or a mixture of amino acids were studied. Controls were 29 normal infants, one to three months of age, fed a standard evaporated milk formula providing 3 to 3.5 g/kg/day of protein (fig. 1 and table II). Results obtained with the lowest protein intake (1.1 g/kg/day) are illustrated in figure 2 and presented in table III. Alterations in the plasma aminogram are noted as early as two days after the reduction in intake and become more pronounced as the feeding is prolonged. The most striking changes are depression of the branched chain amino acids (leucine, isoleucine and valine) and of lysine and tyrosine. Glycine and serine are elevated with glycine showing the greater elevation. Less striking changes are decreased concentrations of threonine, phenylalanine, ornithine, butyrine, cystine and proline.The aminograms obtained with feedings of 1.3 and 1.5 g/kg/day are very similar to those obtained with the more extreme degree of protein reduction ( fig. 3 and table IV). The aminogram after feeding 1.7 g/kg/day remains within the range of average ±1 standard deviation except for the elevation of glycine.A high intake of milk protein, 9 g/kg/day, results in an increase in the levels of a majority of the amino acids ( fig. 5 and table V). The sole exception is glycine, which tends to be low. Marked increases occur in the branched chain amino acids, valine being the most affected; there is also a large increase in the level of proline. The greatest elevations occur in the levels of methionine, which also show the most marked individual variation, elevations ranging from 2 to 35 times normal average value. An apparent tendency of the methionine level to return towards normal with prolonged feeding of the high protein diet is evident on the graph. The significance of this finding must be questioned, however, since the subjects who were maintained the longest on this diet were those who originally did not have the very high levels of methionine.There are some differences in the aminogram when infants are fed the equivalent of 3.5 g/kg/day in the form of amino acids instead of intact protein ( fig. 6 and table VI). On the amino acid diets, lower average plasma values are seen for the branched chain amino acids, alanine, proline, asparagine and citrulline; higher values are observed for threonine and serine. The markedly elevated levels of plasma amino acid observed after feeding 9 g/kg/day of whole protein are not seen after feeding the equivalent amount of nitrogen as an amino acid mixture ( fig. 7 and table VII). There is elevation only of valine and serine. When individual subjects were shifted from the high protein to the high amino acid diet, the pattern shifted within 24 hours. SNYDERMAN, HOLT, NORTON, ROITMAN, PHANSALKAR SpeculationA more precise and sensitive indicator of the state of protein nutrition is needed. While the level of the plasma amino acids changes rapidly with alterations in protein...