Amylase in the Saliva and in the Gastric Aspirates of Premature Infants: Its Potential Role in Glucose Polymer Hydrolysis

Abstract

SummaryAmylase activity was found in saliva from 13 infants, 26-42 wk corrected gestational age. The levels of salivary amylase activity increased with advancing age. In 10 infants, 31-38 wk corrected gestational age (estimated gestational age in wk plus age in wk after birth), gastric aspirates collected before a feeding and sequentially at 30-min intervals after two consecutive feedi n g~ were analyzed for amylase activity and pH. Two different postprandial patterns were obtained. For six of the 10 infants, both the pH and amylase activities of their gastric aspirates showed a distinct maxima at about 60 min after a feeding and a minima at 180 min just before the second feeding. In the remaining four infants, the pHs of their gastric aspirates remained relatively high (5.0-6.0) for the entire postprandial period. In these infants, there was a persistently high level of the amylase activity. In all 10 infants, amylase activity was found in their gastric aspirate samples when the pH was above 3.0. Comparison of the amylase in the gastric aspirate with purified pancreatic and salivary amylases by polyacrylamide gel electrophoresis showed that the amylase in the gastric aspirate has an electrophoretic mobility similar to that of salivary amylase, which suggests a salivary origin. This study supports the possibility that salivary amylase could enter the stomach and retain a significant amount of its activity in premature infants.Starch and glucose polymers are given in some formulas to infants very early in life to accommodate the increased caloric demands. Clinical intolerance to glucose polymers has not been examined sufficiently. Pancreatic amylase is the key enzyme in hydrolysis of glucose polymers. Recognition of intolerance to glucose polymers has been rare in spite of the lack of pancreatic amylase in the duodenal fluids of young infants. In part, this can be due to the existence of alternate pathways with auxiliary enzymes for the hydrolysis of glucose polymers during the physiologic deficiency of pancreatic amylase. The auxiliary enzymes include: salivary amylase, small intestinal brush border glucoamylase and mammary amylase in the breast-fed infant. We have shown that glucoamylase reaches levels similar to those of older children at 1 month of age (13). Two studies have noted the presence of a-amylase in preterm and in term human milk. The ability of milk amylase to survive the gastric environment has been examined and its physiologic importance in the young infant discussed ( 1 1, 16). Recently, we also reported an investigation on the possible role of ingested mammary amylase in the hydrolysis of glucose polymers (1 0). Salivary amylase has been shown to be present in infancy and to reach adult levels much earlier than pancreatic amylase (I, 4, 5, 15, 2 1, 28). The level of salivary amylase in premature infants is however not known. In this study we determined whether the salivary amylase was present and active in gastric fluids during feeding. MATERIALS AND METHODSSubjects. The group of prematures inc...

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“…Amylase activity from the AMY1 gene can be detected in saliva and gastric aspirates of prematurely born infants and the level increases with gestational age from 26 to 42 wk 51. The expression of pancreatic amylase is minimal until weaning introduces non‐milk feeds 50, 51 and the pancreatic gene is probably under partial control by corticosteroids and other hormones 52. Comparing estimates of salivary amylase activity quoted in the literature is complicated by the fact that authors do not always define their units for expressing catalytic activity and different assay temperatures may have been used.…”

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Absorption and Oxidation of Glucose Polymers of Different Lengths in Young Infants

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