1669 ALTERATIONS IN PLASMA AMINO ACIDS IN CHILDHOOD ASTHMA

Abstract

Abnormalities in plasma amino acids (AAs), particularly those related to catecholamine (CTA) or glucose synthesis, may have etiologic or pathogenetic significance in asthma. Plasma AAs and cortisol and urinary CTAs were measured at 8AM and 4PM in randomly selected children with status asthmaticus (n=9;group A), moderately-severe chronic asthma (n=9;group B), mild chronic asthma (n=9;group C) and controls without lung disease (n=7;group D). Group assignment was based on severity of wheezing and medication requirements. All had PaO2>65mmHg. Several conditions believed to alter plasma AAs such as infection and recent corticosteroid use were excluded. AAs were determined chromatographically using an autoanalyzer. Cortisol was measured by competitive protein-binding inhibition, and CTAs were analyzed by spectrophotofluorimetry. Of the 24 AAs analyzed, 11 including tyrosine, proline and alanine were decreased at 8AM or 4PM in group A compared with the other groups (P<0.05). Plasma cortisol was elevated in group A (P<0.05), and urinary CTAs remained unchanged. Normal diurnal variations of AAs and cortisol were preserved. Sequentialdaily determinations in 5 children in group A showed progressive increases in total AA levels as symptoms subsided. Thus certain AAs which are gluconeogenic (proline) or CTA precursors (tyrosine) are decreased in status asthmaticus. Tyrosine deficiency may lead to altered CTA synthesis and play a role in the pathogenesis of asthma. If these findings are confirmed, tyrosine administration may be helpful in therapy of asthma.