Altered Urinary Excretion of Elastin Cross-Links in Premature Infants Who Develop Bronchopulmonary Dysplasia

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Abstract
To determine whether elastin degradation is increased in infants whose respiratory insufficiency required ventilation with high concentrations of O2, the elastin degradation products (desmosines) excreted in the urine of 14 premature male infants during the first 3 wk of life were quantitated by amino acid analysis. Eight of these infants, the "low-O2" infants, did not have severe lung disease and did not require more than 40% O2 beyond the first 8 h of life. The other 6 infants, selected retrospectively because they developed bronchopulmonary dysplasia (BPD), were ventilated with more than 60% O2 for at least the first 72 h of life. The pattern of desmosine excretion observed in infants who developed BPD differed significantly (P < 0.05) from the excretion pattern seen in "low-O2" infants during the first 3 wk of life. At the end of the 1st wk of life, desmosine excretion was significantly greater (P < 0.05) in the infants who later developed BPD than in the "low-O2" infants without severe lung disease. From days 7-9 to 20-22, desmosine excretion increased in the "low-O2" infants from 6.9 .+-. 1.7 .mu.g/kg to 9.0 .+-. 3.5 .mu.g/kg. In contrast, desmosine excretion did not remain elevated in the BPD infants, decreasing from 10.6 .+-. 2.2 .mu.g/kg to 6.1 .+-. 2.9 .mu.g/kg during the same period. In the BPD infants, elevated desmosine excretion through day 9 is likely to reflect lung injury, whereas decreased desmosine excretion beyond day 9 suggests that elastin synthesis and turnover is impaired, possibly as a result of nutritional deficiencies. The observed differences between desmosine excretion patterns in the "low-O2" and BPD infants strongly suggests differences in elastin metabolism in the 2 groups of infants. Elastin may play a critical role in alveolar septal development; therefore, destruction and/or impaired synthesis of elastin might be a causal factor in the impaired lung growth associated with BPD.