Plasma Protease Inhibitors in Premature Infants: Influence of Gestational Age,Postnatal Age,and Health Status 1

Abstract

In newborn infants, the influence of gestational age (GA), postnatal age (PA), and health status on the plasma protease inhibitors α₂-macroglobulin (α₂-M), α,-antitrypsin (α,-AT), C₁ esterase inhibitor (C₁E-INH), α₂-antiplasmin (α₂-AP), and antithrombin III (AT-III) was investigated. Inhibitor levels were measured by radial-immunodiffusion and expressed as a percentage of pooled plasma from adults (mean ± SEM). In total, 54 premature infants (28-36 weeks gestation) were classified at birth as healthy (N = 22) (IV fluids, antibiotics only) or sick (N = 32) (all other support, but excluding infants with disseminated intravascular coagulation (DIC) and studied on Days 1 and/or 7 of life. Healthy term infants (N = 18) and infants with DIC (N = 10) were studied on Day 1 only. All inhibitors except C, E-INH increased with increasing gestational age (P < 0.01). In healthy premature infants all inhibitor levels reached the normal adult range by 1 week of age. In contrast, at 1 week of age, sick infants had lower levels of α₂-M and α₂-AP, and higher levels of α,-AT compared to healthy infants (P < 0.01). The presence of DIC depressed all of the inhibitors on Day 1 except α,-AT when compared to healthy controls (P < 0.01). Thus, gestational age, postnatal age, and health status all significantly influenced the levels of these plasma protease inhibitors.