DIGESTION OF PROTEINS IN HUMAN-MILK, HUMAN-MILK FORTIFIER, AND PRETERM FORMULA IN INFANT RHESUS-MONKEYS

Background: There is limited information in the literature on the capa city of the preterm infant to digest human and bovine milk proteins. W e therefore studied in vivo the luminal phase of the hydrolysis of pro teins in human milk, human milk fortifier, and preterm formula in pret erm rhesus monkeys and in infant rhesus monkeys at 6 weeks and 7 month s of age. Methods: Protein hydrolysis was followed by polyacrylamide g radient gel electrophoresis and electroimmunoassay. The serum level of absorbed unhydrolyzed human or-lactalbumin was measured by a radioimm unoassay method. Trypsin and elastase activities in duodenal contents were measured before and after the meal. Results: In 6-week-old monkey s, the enzyme activities decreased by 50% postprandially, whereas they increased in 7-month-old monkeys. In preterm and in 6-week-old monkey s, hydrolysis of human and bovine whey proteins was slow, and in 6-wee k-old monkeys, 30-50% of the proteins could still be detected immunoch emically in duodenal contents after 60 min. At these ages, serum level s of absorbed alpha-lactalbumin were high. At 7 months of age, no or s mall (lactoferrin and bovine serum albumin) amounts of the proteins co uld be detected in duodenal contents after 15 min. At this age alpha-l actalbumin was not measurable in serum. Conclusion: The low capacity t o digest whey proteins in suckling monkeys may depend upon an immaturi ty of the exocrine pancreas to respond to secretogogues.