Variations of protease inhibitors in foetuses, newborn infants and in some neonatal disorders.

Low levels of protease inhibitors have been found on the 1st day of life in IRDS infants. 19 IRDS infants were studied together with foetuses and control term and preterm infants. Alpha1-antitrypsin, antichymotrypsin and alpha2-macroglobulin were measured with the electroimmuno assay. IRDS infants had significantly reduced concentration of alpha-antitrypsin and antichymotrypsin on the 1st day, the level increasing to normal on the 2nd day. In foetuses alpha1-antitrypsin was normal, antichymotrypsin 2% and alpha2-macroglobulin 1/3 of the normal adult level. The protease inhibitors are increased in infants born after premature rupture of foetal membranes. The part, if any, played by protease inhibitors is not entirely understood. The inhibitors may, theoretically, be of some importance in the dissolution of the hyaline membranes, protect against pulmonary vasoconstriction, protect pulmonary tissue against leucocyte and macrophage proteolytic enzymes and inhibit the release of or counteract vasoactive substances that might take part in the development of shock in IRDS babies.