Acta Paediatr 81: 436-8. 1992
SHORT COMMUNICATION
The urinary acylcarnitine profile in three cases of transient hyperammonemia of the newborn Toru Sakuma, Naruji Sugiyama and Yoshiro Wada Department of Pediatrics. Nagoya City University Medical School I Mizuho-cho, Mizuho-ku, Nagoya 467, Japan
Sodium benzoate is generally administered to the patient with hyperammonemia that develops as a consequence of an inherited defect in one of the enzymes of the urea cycle (1, 2). Although the pathogenesis of transient hyperammonemia of the newborn is obscure, it is known that sodium benzoate is also effective in reducing the blood concentration of ammonia in this condition (1). The usual dose of sodium benzoate used is thought to be safe but the possibility of benzoate toxicity has been reported in an animal model (3). Patient 1. After an uncomplicated pregnancy, a 201 6g, 34-weeks’ gestation, male infant was born to a 24year-old primigravida. Apgar score was 9 at 1 min. At 3 h there was respiratory distress and mandatory ventilation was required at the age of 7 h. Blood ammonia was 685.3 pmol/l at 20 h. Exchange transfusion was followed by peritoneal dialysis and iv administration of Larginine (1OO mg/kg/day). After continuous dialysis, the infant responded to stimuli and blood ammonia decreased below 176.5 pmol/l. Open-liver biopsy was performed at the age of three months. The laboratory studies before treatment including electrolytes, lipids and liver function test were unremarkable. Blood and cerebrospinal cultures were negative. Blood sugar was 38 mg/100 ml. Plasma arginine was 29.8 ,umol/l (normal: 64.6-97.8 pmol/l) and other amino acids were also normal. Analysis of urinary orotic acid was 10 pmol/ g.Cr (normal: less than 20 pmol/g.Cr). Urea cycle enzyme activities were normal. Patient 2. This 2500-g male infant was born to a second gravida at 35 weeks’ gestation. Apgar score was 9 at 1 min. Respiratory distress and lethargy developed at 20 h. Blood ammonia was 467.7 pmol/l. Exchange transfusion and continuous peritoneal dialysis were performed, followed by iv administration of arginine and sodium benzoate (100 mg/kg/day, 200 mg/kg/day, respectively). Blood ammonia concentration increased to 4778.8 pmol/l at 80 h postnatally and then normalized gradually. Blood ammonia no longer increased. Openliver biopsy was performed at the age of three months. Laboratory studies at admission were unremarkable. Blood sugar was 21.5 mg/l00 ml. The cultures were negative. Plasma arginine was 34.5 pmol/l. Other plasma amino acid, organic acid and urinary orotic acid levels were normal, as were urea cycle enzyme levels. Patient 3. A 2944-g male infant was born after an uncomplicated 38-week gestation to a 24-year-old primigravida. Apgar score was 8 at 1 min. The infant had
frequent apnea attacks, became hypotonic at 33 h, and was intubated and attached to a ventilator. Blood ammonia was greater than 588.2 pmol/l at 45 h. Exchange transfusion was given following administration of sodium benzoate, arginine and L-carnitine at 200, 200 and 70 mg/kg/day, respectively. Thereafter, blood ammonia decreased below 58.7 pmol/l. Hyperammonemia did not return. Analyses of plasma amino acid and organic acid concentrations were normal except for mild depletion of citrulline (5.5 pmol/l; control: 20-30 pmol/l). Plasma arginine was 26.5 pmol/l. No increase in urinary orotic acid was detected and the maximum level was 9.7 pmol/g.Cr. Liver function tests were normal and cultures were negative. A urea cycle enzyme was not assayed. Echography of the liver was normal. Urine samples stored at - 20°C were used to assay the urinary acylcarnitine profile with fast atom bombardment-mass spectrometry as described previously (4). Urinary hippurate was also quantified in the urine samples with salicylurate added (1 pmol/ml) as the internal standard. Figure 1 shows the blood concentration of ammonia, urinary acylcarnitines and hippurate in patient 1. Although sodium benzoate was not administered, the concentrations of hippurate and benzoylcarnitine in urine were much higher than those of the controls (hippurate: 56 24 pmol/g.Cr; benzoylcarnitine: 2.2 f 0.6 pmol/g.Cr). The blood concentration of ammonia and the urinary hippurate concentration decreased rapidly after 12 h of continuous peritoneal dialysis. The urinary excretion of propionylcarnitine was higher than in controls (8.4f2.1 pmol/g.Cr). The ratio of the acetylcarnitine/propionylcarnitineconcentration in urine was 0.74 (normal: 2.2f0.7). Urinary free carnitine concentration was 47.1 pmol/g.Cr (control: 133.5f 66.0 pmol/g.Cr). Patient 2 was treated with sodium benzoate and arginine. Before administration of sodium benzoate, the urine concentrations of hippurate, benzoylcarnitine and propionylcarnitine were higher than those of controls. The ratio of the acetylcarnitine/ propionylcarnitine concentration was 0.65. Urinary free carnitine concentration was 42.6 pmol/g.Cr. Patient 3 was treated with sodium benzoate, arginine and Lcarnitine. The excretion patterns of acetylcarnitine, propionylcarnitine, benzoylcarnitine and hippurate were similar to those in patients 1 and 2. The urinary free carnitine was 33.4 pmol/g.Cr. Three days after labor, the mother’s urine showed a hippurate concentration of
+
Hyperammonemia in the newborn
ACTA PKDIATR 8 I ( I 992)
437
Transient hyperammonemia of the newborn case 1
n
Coma Respiratory distress
'1,
500
Peritoneal diaiysis
I
Arglnine l m / k e / d a y
] (mmo I A.Cr 1
E 400 -
0 Acetylcarmitine
500
Proplanylcamitine
al C
R
I ,
2 300 0
2 Q
2 200 Q C
'r 100 3
-
OL
A Benzoylcamitlne A Hlppurate
al
- 20 5 2
- 15 rn
- 10 $ .-C - 55 - 0
Fig. I. Clinical course of patient 1. Maximum daily blood ammonia concentrationis shown. Exchange transfusion (200 ml/kg) is indicated by the arrows.
1124 pmol/g.Cr (matched control: 560k 174 pmol/ g.Cr). Since there was much more excretion of propionylcarnitine and relatively low excretion of free carnitine in all our cases compared with the controls, it was speculated that the change in mitochondria1 acylcarnitine profile (i.e. alteration in CoA profile) had taken place before treatment. Although plasma free carnitine was not examined, it was suspected that there was at least hypocarnitinemia in all cases because of the hypocarnitinuria. The cause of the altered acylcarnitine profiles was obscure, but urinary hippurate and benzoylcarnitine
concentrations were high in all cases. Moreover, the urinary hippurate concentration was very high in the mother of patient 3. A possible cause was the alteration of the acyl-CoA profile induced by benzoyl-CoA production. Carnitine is a buffer to correct for an abnormal CoA profile in mitochondria. The synergism of carnitine deficiency and altered CoA profile such as low acetylCoA may be important factors in inhibiting carbamyl phosphate production (5, 6). The addition of L-carnitine in this disease with or without sodium benzoate was necessary not only to reduce side effects but also to improve ammonia excretion.
438
T Sakuma et al.
ACTA PEDIATR 81 (1992)
References 1. Ballard RA, Vinocur B, Reynolds JW, et al. Transient hyperammo-
nemia of the preterm infants. N Engl J Med 1978;299:920-5 2. Brusilow SW, Valle DL, Batshaw ML. New pathway of nitrogen excretion in inborn errors of urea synthesis. Lancet 1979;2:4524 3. O'Connor JE, Costell M, Glisolia S. The potentiation of ammonia toxicity by sodium benzoate is prevented by L-carnitine. Biochem Biophys Res Commun 1987;1459 17-24 4. Sakuma T, Asai K, Sugiyama N, et al. The identification of benzoylcarnitine in the urine of a patient of hyperammonemia. Tohoku J Exp Med 1989;159:147-51
5. Cohen MS, Cheung CW, Raijman L. The effects of ornithine on mitochondria1 carbamyl phosphate synthesis. J Biol Chem 1980;255:10248-55 6. Bachmann C, Schubigger G, Jaggi KH, et al. N-acetylglutamate synthetase deficiency;a new disorder ofammonia detoxification. N Engl J Med 1981;304:543
Received February 27, 1991. Accepted June 19, 1991
SHORT COMMUNICATION
The urinary acylcarnitine profile in three cases of transient hyperammonemia of the newborn Toru Sakuma, Naruji Sugiyama and Yoshiro Wada Department of Pediatrics. Nagoya City University Medical School I Mizuho-cho, Mizuho-ku, Nagoya 467, Japan
Sodium benzoate is generally administered to the patient with hyperammonemia that develops as a consequence of an inherited defect in one of the enzymes of the urea cycle (1, 2). Although the pathogenesis of transient hyperammonemia of the newborn is obscure, it is known that sodium benzoate is also effective in reducing the blood concentration of ammonia in this condition (1). The usual dose of sodium benzoate used is thought to be safe but the possibility of benzoate toxicity has been reported in an animal model (3). Patient 1. After an uncomplicated pregnancy, a 201 6g, 34-weeks’ gestation, male infant was born to a 24year-old primigravida. Apgar score was 9 at 1 min. At 3 h there was respiratory distress and mandatory ventilation was required at the age of 7 h. Blood ammonia was 685.3 pmol/l at 20 h. Exchange transfusion was followed by peritoneal dialysis and iv administration of Larginine (1OO mg/kg/day). After continuous dialysis, the infant responded to stimuli and blood ammonia decreased below 176.5 pmol/l. Open-liver biopsy was performed at the age of three months. The laboratory studies before treatment including electrolytes, lipids and liver function test were unremarkable. Blood and cerebrospinal cultures were negative. Blood sugar was 38 mg/100 ml. Plasma arginine was 29.8 ,umol/l (normal: 64.6-97.8 pmol/l) and other amino acids were also normal. Analysis of urinary orotic acid was 10 pmol/ g.Cr (normal: less than 20 pmol/g.Cr). Urea cycle enzyme activities were normal. Patient 2. This 2500-g male infant was born to a second gravida at 35 weeks’ gestation. Apgar score was 9 at 1 min. Respiratory distress and lethargy developed at 20 h. Blood ammonia was 467.7 pmol/l. Exchange transfusion and continuous peritoneal dialysis were performed, followed by iv administration of arginine and sodium benzoate (100 mg/kg/day, 200 mg/kg/day, respectively). Blood ammonia concentration increased to 4778.8 pmol/l at 80 h postnatally and then normalized gradually. Blood ammonia no longer increased. Openliver biopsy was performed at the age of three months. Laboratory studies at admission were unremarkable. Blood sugar was 21.5 mg/l00 ml. The cultures were negative. Plasma arginine was 34.5 pmol/l. Other plasma amino acid, organic acid and urinary orotic acid levels were normal, as were urea cycle enzyme levels. Patient 3. A 2944-g male infant was born after an uncomplicated 38-week gestation to a 24-year-old primigravida. Apgar score was 8 at 1 min. The infant had
frequent apnea attacks, became hypotonic at 33 h, and was intubated and attached to a ventilator. Blood ammonia was greater than 588.2 pmol/l at 45 h. Exchange transfusion was given following administration of sodium benzoate, arginine and L-carnitine at 200, 200 and 70 mg/kg/day, respectively. Thereafter, blood ammonia decreased below 58.7 pmol/l. Hyperammonemia did not return. Analyses of plasma amino acid and organic acid concentrations were normal except for mild depletion of citrulline (5.5 pmol/l; control: 20-30 pmol/l). Plasma arginine was 26.5 pmol/l. No increase in urinary orotic acid was detected and the maximum level was 9.7 pmol/g.Cr. Liver function tests were normal and cultures were negative. A urea cycle enzyme was not assayed. Echography of the liver was normal. Urine samples stored at - 20°C were used to assay the urinary acylcarnitine profile with fast atom bombardment-mass spectrometry as described previously (4). Urinary hippurate was also quantified in the urine samples with salicylurate added (1 pmol/ml) as the internal standard. Figure 1 shows the blood concentration of ammonia, urinary acylcarnitines and hippurate in patient 1. Although sodium benzoate was not administered, the concentrations of hippurate and benzoylcarnitine in urine were much higher than those of the controls (hippurate: 56 24 pmol/g.Cr; benzoylcarnitine: 2.2 f 0.6 pmol/g.Cr). The blood concentration of ammonia and the urinary hippurate concentration decreased rapidly after 12 h of continuous peritoneal dialysis. The urinary excretion of propionylcarnitine was higher than in controls (8.4f2.1 pmol/g.Cr). The ratio of the acetylcarnitine/propionylcarnitineconcentration in urine was 0.74 (normal: 2.2f0.7). Urinary free carnitine concentration was 47.1 pmol/g.Cr (control: 133.5f 66.0 pmol/g.Cr). Patient 2 was treated with sodium benzoate and arginine. Before administration of sodium benzoate, the urine concentrations of hippurate, benzoylcarnitine and propionylcarnitine were higher than those of controls. The ratio of the acetylcarnitine/ propionylcarnitine concentration was 0.65. Urinary free carnitine concentration was 42.6 pmol/g.Cr. Patient 3 was treated with sodium benzoate, arginine and Lcarnitine. The excretion patterns of acetylcarnitine, propionylcarnitine, benzoylcarnitine and hippurate were similar to those in patients 1 and 2. The urinary free carnitine was 33.4 pmol/g.Cr. Three days after labor, the mother’s urine showed a hippurate concentration of
+
Hyperammonemia in the newborn
ACTA PKDIATR 8 I ( I 992)
437
Transient hyperammonemia of the newborn case 1
n
Coma Respiratory distress
'1,
500
Peritoneal diaiysis
I
Arglnine l m / k e / d a y
] (mmo I A.Cr 1
E 400 -
0 Acetylcarmitine
500
Proplanylcamitine
al C
R
I ,
2 300 0
2 Q
2 200 Q C
'r 100 3
-
OL
A Benzoylcamitlne A Hlppurate
al
- 20 5 2
- 15 rn
- 10 $ .-C - 55 - 0
Fig. I. Clinical course of patient 1. Maximum daily blood ammonia concentrationis shown. Exchange transfusion (200 ml/kg) is indicated by the arrows.
1124 pmol/g.Cr (matched control: 560k 174 pmol/ g.Cr). Since there was much more excretion of propionylcarnitine and relatively low excretion of free carnitine in all our cases compared with the controls, it was speculated that the change in mitochondria1 acylcarnitine profile (i.e. alteration in CoA profile) had taken place before treatment. Although plasma free carnitine was not examined, it was suspected that there was at least hypocarnitinemia in all cases because of the hypocarnitinuria. The cause of the altered acylcarnitine profiles was obscure, but urinary hippurate and benzoylcarnitine
concentrations were high in all cases. Moreover, the urinary hippurate concentration was very high in the mother of patient 3. A possible cause was the alteration of the acyl-CoA profile induced by benzoyl-CoA production. Carnitine is a buffer to correct for an abnormal CoA profile in mitochondria. The synergism of carnitine deficiency and altered CoA profile such as low acetylCoA may be important factors in inhibiting carbamyl phosphate production (5, 6). The addition of L-carnitine in this disease with or without sodium benzoate was necessary not only to reduce side effects but also to improve ammonia excretion.
438
T Sakuma et al.
ACTA PEDIATR 81 (1992)
References 1. Ballard RA, Vinocur B, Reynolds JW, et al. Transient hyperammo-
nemia of the preterm infants. N Engl J Med 1978;299:920-5 2. Brusilow SW, Valle DL, Batshaw ML. New pathway of nitrogen excretion in inborn errors of urea synthesis. Lancet 1979;2:4524 3. O'Connor JE, Costell M, Glisolia S. The potentiation of ammonia toxicity by sodium benzoate is prevented by L-carnitine. Biochem Biophys Res Commun 1987;1459 17-24 4. Sakuma T, Asai K, Sugiyama N, et al. The identification of benzoylcarnitine in the urine of a patient of hyperammonemia. Tohoku J Exp Med 1989;159:147-51
5. Cohen MS, Cheung CW, Raijman L. The effects of ornithine on mitochondria1 carbamyl phosphate synthesis. J Biol Chem 1980;255:10248-55 6. Bachmann C, Schubigger G, Jaggi KH, et al. N-acetylglutamate synthetase deficiency;a new disorder ofammonia detoxification. N Engl J Med 1981;304:543
Received February 27, 1991. Accepted June 19, 1991
