Carnitine status and blood ammonium levels in low birth weight infants.
Forty-three low birth weight infants appropriate for gestational age (AGA) were monitored to evaluate carnitine status in relation to blood ammonium levels. The infants were grouped into three depending on blood ammonium level on postnatal day 7: 62.9 +/- 3.8 mumol/L in group 1 (N = 13), 38.9 +/- 8.4 mumol/L in group 2 (N = 23), and 24.5 +/- 2.9 mumol/L in group 3 (N = 9). Plasma free carnitine levels decreased in all three groups (p less than 0.001) and plasma short chain acylcarnitine increased only in group 1 (p less than 0.002), compared to findings in normal infants. The blood ammonium level positively and negatively correlated to plasma short chain acylcarnitine (p less than 0.002) and plasma free carnitine levels (p less than 0.002), respectively. The reabsorption rate of free carnitine in renal tubules (RRFC) was decreased at rates of 37.5, 27.5, and 25% of infants in groups 1, 2, and 3, respectively. The acylcarnitine/free carnitine clearance ratio (RAFCC) was decreased in groups 1 (p less than 0.01) and 2 (p less than 0.05) compared with group 3. Thus, an accumulation of short chain acyl moieties and insufficiency in renal absorption of free carnitine are putative causes of lowered plasma free carnitine in infants with higher blood levels of ammonium. The possibility that the carnitine status regulates blood ammonium levels in low birth weight infants warrants continued investigation.
Nakamura
T
T
Department of Pediatrics, Kumamoto University Medical School, Japan.
Nakamura
S
S
Kondo
Y
Y
Ikeda
T
T
Ogata
T
T
Endo
F
F
Matsuda
I
I
D000641:Ammonia / Q000097:blood*; D002331:Carnitine / Q000097:blood / Q000378:metabolism* / Q000652:urine; D005069:Evaluation Studies as Topic; D006801:Humans; D007230:Infant, Low Birth Weight / Q000378:metabolism*; D007231:Infant, Newborn
D000641:Ammonia; D002331:Carnitine