Lipoprotein and hepatic lipase activities in postheparin plasma of preterm infants

Abstract

Fat tolerance tests suggest that the disposal of lipids infused is slower in preterm than term infants. This has been attributed to low lipoprotein lipase activity because postheparin lipolytic activity (PHLA) has been found to be low in very-low-birth-weight infants. Hepatic lipase, however, accounts for about 70% of PHLA, which makes PHLA an inadequate measure of lipoprotein lipase. With specific methods we measured lipoprotein lipase and hepatic lipase activities in postheparin plasma of eleven preterm neonates. Blood samples were taken fifteen minutes after a heparin bolus of 100 IU/kg given before an exchange transfusion performed with fresh heparinized blood because of hyperbilirubinemia, blood group incompatibility or sepsis. The infants were 1-4 days old and had birth weights (range 1210-3490 gm) appropriate for gestational age (range 28-36 weeks). Eight infants (group 1) were in good clinical condition while three infants (group 2) suffered from septic shock. In group 1 lipoprotein and hepatic lipase activities were 27 and 64 μmol FFA/ml/h; both are higher than the activities found in term infants (Rovamo et al. 1984 Pediatr. Res. in press). In group 2 lipoprotein and hepatic lipase activities were 1.8 and 11 μmol FFA/ ml/h; both are considerably lower than the activities found in Group 1. Our results indicate that lipoprotein lipase is not the reason for slow clearance of fat from the circulation in preterm infants except in septic shock.