Trypsin and elastase activity in duodenal juice from preterm infants before and after a meal of human milk

Objective To analyze trypsin and elastase in duodenal juice before and afte r a human milk meal using esterolytic and immunochemical methods in preterm infants. Patients and methods Eighteen preterm infants, born at a gestational age of 23-30 weeks, were studied at an age of 1-2 months. Duodenal juice was coll ected before and up to 120 min after a meal of human milk. Trypsin activity was determined with N-benzoyl-DL-arginine-p-nitroanilide and elastase acti vity with succinyl-trialanine-p-nitroanilide as substrate. The presence of anionic and cationic trypsins and elastases was studied by immunoelectropho resis. Results Before the meal, trypsin activity was 132 mu g/ml (mean value) corr esponding to about 20% of that in older children. Corresponding figures for elastase were 0.6 mu g/ml and 50%. After the meal, trypsin activity decrea sed to about 55 mu g/ml at 30, 60 and 90 min; at 120 min it increased to 12 1 mu g/ml. The elastase activity was not influenced by the meal. Immunoelec trophoresis showed that, in samples with 'normal' activity, the anionic and cationic trypsins were located at their 'normal' places. In 12 out of 13 s amples with low or no trypsin activity after the meal, the trypsin precipit ates had moved towards the slit, indicating complexation. Precipitate again st cationic elastase was not detectable in 15 out of fti infants. Precipita te against anionic elastase was present in all samples. Conclusion In preterm infants of 28-36 weeks of postconceptional age prepra ndial trypsin and elastase activities were 20% and 50%, respectively, of th ose in older children. Trypsin activity decreased postprandially to low lev els (about 60%). Preliminary results indicate that this may be due to the f ormation of a complex between trypsin and protein(s) in human milk. Cationi c elastase is not developed in preterm infants. These findings may imply th at protein digestion is compromised in the preterm infant.