RESUMO
The inhibitory and specific activities of serum alpha 1-antitrypsin (1-AT) at pH levels of 8.20, 7.45, 7.35, 7.25 and 7.15, were studied in 66 neonates with idiopathic respiratory distress syndrome (IRDS) and in 82 healthy neonates. In vivo pH values were also correlated in both groups with the specific and inhibitory activities of 1-AT. Comparisons between healthy neonates and neonates with IRDS showed that in the latter, the inhibitory and specific activities of 1-AT were lower, with every pH assayed, together with twice a percentual decrease from pH 8.20 to pH 7.15 in both activities. No statistical correlation was established in the in vivo pH of infants in both groups with the inhibitory and specific activities of 1-AT. Results suggest two alternatives. The first one related to a molecular structure different from 1-AT in infants with IRDS, and the second one regarding changes in 1-AT produced by partial breakdown or modified by hypoxia, acidosis or both.
Assuntos
Síndrome do Desconforto Respiratório do Recém-Nascido/enzimologia , alfa 1-Antitripsina/sangue , Ativação Enzimática , Humanos , Concentração de Íons de Hidrogênio , Recém-NascidoRESUMO
In two groups of neonates serum concentrations of alpha-1-antitrypsin (1-AT) were determined by means of radial immunodiffusion, and 1-AT inhibitory capacity determinations were made using benzoyl-1-arginine-p-nitroanilide as a substrate. There were 66 children in the first group of neonates with idiopathic respiratory distress syndrome (IRDS), and 82 healthy children in the second group with birth weight and gestational and post natal ages similar to those of neonates with IRDS. In the latter, 1-AT concentration and inhibitory activity levels were lower than those found in healthy children; these differences were statistically significant. These findings explain both the retardation in the lysis of the hyaline membrane and the fact that a decrease in serum 1-AT levels elicits lung tissue damage by the action of proteolytic enzymes contained in leucocytes.