Submitted to: Pediatric Research
Publication Type: Abstract Only
Publication Acceptance Date: February 14, 2000
Publication Date: N/A
Technical Abstract: To determine if CYS-supplementation of parenteral nutrition infusates increases endogenous synthesis of TAU and GSH conversion of CYS to TAU as well as erythrocyte GSH, synthesis and concentration were measured in premature neonates assigned randomly to receive CYS-supplemented (Group 1) vs. CYS-free (Group 2) parenteral nutrition infusates. Mean birth weight and gestational age of the two groups did not differ. At study time, all had received parenteral nutrients exclusively for 5.7+/-1.6d and 6.6+/- 1.9d, respectively. Mean energy and amino acid intakes of Group 1 were 92+/-11 kcal/kg/d and 2.9+/-0.4 g/kg/d; those of Group 2 were 96+/-14 kcal/kg/d and 2.7+/-0.4 g/kg/d. Each infant received a 6-hr primed, constant infusion of 2H2-CYS, 15N-TAU and U-13C-glycine. Endogenous TAU synthesis was determined from plasma enrichment of 2H2-TAU. The fractional rate of synthesis (FRS) of GSH was determined from incorporation of U-13C- glycine into GSH between 4 and 6 hrs; erythrocyte free glycine was assumed to be the precursor. Erythrocyte GSH concentration was determined by HPLC. Endogenous synthesis of TAU was 8.5+/-3.0 mumols/kg/h in Group 1 and 5.0 mumoles/kg/h in Group 2 representing 19.6+/-4.6% and 9.5+/-4.5% of 15N-TAU flux, respectively. The FSR of GSH was 77.7+/-9.6%/d in Group 1 and 46.9+/- 3.0%/d in Group 2 and absolute rates of GSH synthesis were 0.49+/-0.06 mmols/L/d and 0.27 mmols/L/d, respectively. Despite this, erythrocyte GSH concentration of neither group differed. We conclude that supplementation of nutriton regimens with CYS increases endogenous synthesis of TAU and GSH but does not increase erythrocyte GSH concentration. The higher rate of GSH synthesis without a difference in concentration suggests that the newly synthesized GSH was utilized for antioxidant defense.