725 Lymphocyte Respiration in Children with Trisomy 21

Aims This study aimed to measure lymphocyte mitochondrial O 2 consumption (cellular respiration) in children with trisomy 21. Methods Peripheral blood mononuclear cells were isolated from whole blood of trisomy 21 and control children and immediately used to measure the respiratory rate. [O 2 ] was determined as function of time from the phosphorescence decay rates (1/t) of Pd (II)-meso-tetra-(4-sulfonatophenyl)-tetrabenzoporphyrin. In sealed vials containing cells and glucose as a respiratory substrate, [O 2 ] declined linearly with time, confirming the zero-order kinetics of O 2 consumption (conversion to H 2 O) by cytochrome oxidase. Results The rate of respiration (k, in mM O 2 per min), thus, was the negative of the slope of [O 2 ] vs. time. NaCN inhibited O 2 consumption, confirming the oxidation occurred in the mitochondrial respiratory chain. For control children (age = 8.8±5.6 yr, n=26), the mean (± SD) value of k c (in mM O 2 per min per 10 7 cells) was 1.36±0.79 (coefficient of variation = 58%; median = 1.17; range = 0.60 to 3.12; –2SD = 0.61). For children with trisomy 21 (age = 7.2±4.6 yr, n=26), the value of k c was 0.82±0.62 (coefficient of variation = 76%; median = 0.60; range = 0.20 to 2.80), p k c values of 0.20 to 0.60 (i.e., Conclusion Thus, it appears that some children with trisomy 21 have relatively reduced lymphocyte bioenergetics. The biological implication of this finding (variation) requires further studies.