Abstract
Introduction: Due to low solubility of the (semi-)essential amino acids Tyrosine (Tyr) and Cysteine (Cys-ss-Cys) and to stability problems with Cysteine (Cys) some AA solutions contain acetylated Tyr and Cys. We compared plasma AA levels in 2 groups of preterm infants fed two comercially available AA solutions different in way of offering Tyr and Cys.
Patients and Methods: Infants on TPN were studied on day 7 of life. Group A (n=5, birthweight 1.41±0.32 kg, gest. age 31±2 wk, study weight 1.37±0.32 kg) was fed 2.5±0.3 g AA -and 63±11 kcal/kg.d, with acetylated Tyr and Cys. Group B (n=4, bw 1.34±0.43 kg, ga 30±2 wk, sw 1.28±0.33 kg) received 2.1±0.2 g AA -and 62±5 kcal/kg.d with maximal concentrations of free Tyr and Cys. AA levels were Measured by HPLC.
Results:
Normal range in breastfed term infants is Tyr: 38-119 μmol/L and Cys: 35-69 μmol/L. Urinary excretion for NAT was 281±108, for AC 28±5 μmol/kg.d. in group A.
Conclusions: 1. By administering acetylated Tyr and Cys (group A), plasma levels of NAT and AC are higher than those of free Tyr and Cys. Cystine levels in 3 out of 6 patients were detected in trace amounts only. Almost 40% of administered NAT and more than 50% of AC was excreted in urine. 2. Tyr and Cys administered in dosages as in group B resulted in plasma levels below reference value. 3. Both ways of administration do not provide in reference Tyr and Cys levels. 4. Results indicate that both ac Cys and ac Tyr are not appropriate substrates to supply the corresponding free amino acids.
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Van Goudoever, J., Sulkers, E., Broerse, H. et al. N-ACETYL-TYROSINE (NAT) AND ACETYL-CYSTINE (AC): AN ALTERNATIVE TO LOW INTAKE OF TYROSINE AND CYSTINE IN NEONTAL TOTAL PARENTERAL NUTRITION (TPN)?. Pediatr Res 32, 626 (1992). https://doi.org/10.1203/00006450-199211000-00130
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DOI: https://doi.org/10.1203/00006450-199211000-00130